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The Lemur SafeDriver can be installed by anyone in no more than a couple of minutes, and operates in virtually every vehicle made after 1996.

While not monitoring as comprehensive a set of driving data as some of the other units available, it is also only a tenth the price of some others, and happily does not have the $30 - $50/month monitoring fee either.

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Lemur SafeDriver Review part 2

Using the system and trying to cheat its monitoring

The sensor/transmitter is quite literally a 'black box' that simply plugs into your vehicle's OBD-II port and then transmits data to the fob/receiver unit.

Part 2 of a two part review of the Lemur SafeDriver system.  Please see part 1 for an explanation of what the SafeDriver is, what it does and how and why.



The Lemur SafeDriver system elegantly combines simplicity with affordability.  It does not pretend to be a fully featured monitoring system and it does not give you a vast array of data about the monitored vehicle and driver's performance, but it gives you enough for a vague approximate understanding of what is going on, and - perhaps most valuably - introduces an element of accountability into your teen's driving behavior.

It has a recommended retail price of $69.95 and is available from Amazon, currently  for $56.13.  There are no ongoing monthly costs.

A great little gadget, possibly for yourself, or for anyone with teenage drivers.

Using the SafeDriver

(Please see the first part of this review for introductory comments, description, etc, of the unit.)

Using the SafeDriver is very simple.  Once installed, the sensor/transmitter is always either in a standby mode or an 'on/transmitting' mode.  There is nothing to switch on/off, and nothing else you need to do or activate or remember.

Because of the sensor expecting to be always connected, if the unit is ever disconnected, its state changes from on or standby to off/disconnected, and so when it is reconnected again, it sends an 'I was unplugged' warning to the fob/receiver.  Of course, most of the time, such a message indicates that someone was trying to cheat the system.

The only possible valid indicator would be if the vehicle's battery was removed so that the sensor loses all standby power - it would not be able to distinguish between this and a disconnect.  But of course, it is unlikely that there's be a bona fide battery removal during the course of an ordinary day's driving by someone you are wishing to monitor.

If the fob is in the car while it is being driven, it gets updates every 30 seconds to update its data.  You can also force an update simply by pressing its reset button if you can't wait 30 seconds - this was helpful for me when testing the unit, but it is probably not something you'd need to do much in ordinary use.

A good added feature is that it is possible to operate the car without the fob/receiver being present.  When the fob is then reunited with the car subsequently, the transmitter will update the fob with all the data it had missed.

The sensor/transmitter is storing the information that it downloads to the receiver/fob when the two are able to communicate each other, and the sensor unit has enough storage capacity to save trip information up to 9999 miles and up to 99 braking events (plus of course whatever the maximum speed is since it was last reset).  So you could lend your car to someone for weeks at a time and still get a full update of driving data when you (and the receiver/fob) are reunited with the vehicle subsequently.

Car Battery Drain

The sensor/transmitter is always on, and so is always taking a small amount of power from the vehicle's battery.

The amount of power being taken depends on the vehicle and its particular type of OBD-II implementation, but most more modern vehicles (using the CAN type of OBD-II data, in case you wondered) will experience a 9.5 mA power drain.

What does this mean?  It means that the SafeDriver is drawing just under a quarter of an amp hour of battery power per day.  If you had your car parked for two weeks at the airport, the unit would have drawn 3.2 amp hours of power during that two week period.  Most car batteries store something in excess of 50 amp hours of charge, so the current drain by the SafeDriver is unlikely to result in draining the battery significantly for all normal periods of inactivity.

Accuracy of the Data Reported

The information reported by the SafeDriver unit was close to exactly the same as the data in the car - unsurprising because they were both using the same 'raw data' from the car's computer.

I also matched it against a GPS unit, and again found a close match in values.

The SafeDriver slightly under-reported on maximum speed (by perhaps 2 mph) but this is probably due to a discrepancy between the vehicle's speed sensor and the GPS speed calculation rather than due to any errors in how the SafeDriver itself calculates/displays such things.

Trying to 'Cheat' the SafeDriver

Is it possible to cheat the SafeDriver system and avoid its telltale monitoring?  I tested six scenarios.

First, I drove somewhere without the receiver with me.  When I returned, the receiver downloaded the data from my travels and updated itself with a new display of max speed, miles traveled and number of sudden brakings.  So the first strategy to avoid the scrutiny of the SafeDriver system failed.

Second, I unplugged the transmitter, went for a drive, then plugged the transmitter back in again.  The system couldn't then update itself with data it had never received, but it displayed a prominent 'Tamper' alert on the receiver's display.  So the second strategy failed to avoid the scrutiny of the system too.

Third, I removed the battery from the Transmitter, drove somewhere, then replaced it again.  This caused the transmitter to lose all data and reset itself, and to again display a 'Tamper' alert.  A third failure to cheat the system.

There may be other ways to cheat the system, but they would involve major brain surgery inside the car's computer system and cutting wires to the OBD-II port, which was definitely not something I wanted to trial.

So it seems fair to pronounce the system reasonably tamper-proof from most moderate level attempts at breaking its security.

There are two more forms of cheating that I also tested.

The first was to only very briefly speed up to set a new maximum speed, then to immediately reduce the speed again.  This was a test to see if the unit was sending out lots of short duration samples to accurately depict even short maximum speeds, or if it was perhaps sending out an average speed reading once every 30 seconds during its regular handshake/synch between transmitter and receiver.

Using both the GPS and speedometer to measure an instantaneous maximum speed, I got the car briefly to a certain speed where we need not publicly disclose the first digit, but the second digit displayed on the GPS came to a 7.5 - think of it, perhaps, as 27.5 mph - a speed which closely correlated with the more approximate indication on the analog speedometer.  With the GPS having a short interval of sampling/averaging error itself, it is probably reasonable to assume the true maximum speed briefly reached was perhaps(2)8 or (2)9 mph.

The SafeDriver reported a maximum speed of (2)6 mph.  So there was a very slight degree of under-reporting, but there are also very few scenarios where even a wild and crazy teenager would roar at full throttle up to a high speed then immediately take his (her?) foot off the gas pedal and stomp down on the brake pedal, so this mild under-read does not seem serious.

Further testing showed that the SafeDriver always slightly under-reported the maximum speed (or possibly the GPS slightly over-reports the maximum speed), so this was hardly a successful cheat at all.

The final form of cheating was to see what would happen if I only slowed down perhaps 12 mph rather than 15+ mph, but in a very brief interval of time so as to be braking at a rate much harder than losing 15 mph in 2 seconds.

With lovely new tires, automatic brake assist, traction control and ABS, the Landrover responded enthusiastically to my panic stop, and I sliced about 12 mph off the vehicle's speed in less than a second, only to then immediately release the brake pedal and stop on the gas again to ensure I didn't continue to inadvertently decelerate past the magic 15 mph number that I knew would for sure trigger a 'Sudden Brake' report on the unit.

This sort of cheat process did work.  The unit seems to simply track the speed in a rolling two second period, and is only concerned if there is a total reduction of 15 + mph in less than two seconds.

This is not really a loophole.  Trust me when I say it is very hard to panic brake and 'only' lose 12 mph in the process!

So not only can one not totally defeat the SafeDriver's reporting, one can also not skew its reporting to make it materially under-report the driving data it is monitoring.

There is another way to try and cheat the system - and that would be simply to reset the unit.  However, resetting the unit requires a knowledge of the secret passcode, and so that makes it difficult rather than easy to reset it.

Besides which, if you did reset the unit, two things would happen.  First, you'd also be resetting the miles traveled measure, which could cause an obviously wrong value to be displayed there.  Second, the system actually counts the number of times it has been reset, so that would increase the count of resets, which you may or may not ever notice.

The password is only semi-secret.  You can download the instruction sheet for the unit from the manufacturer's website, and both the standard reset and the absolute master system password are both printed on there, so a highly motivated person trying to cheat the system could obtain both passcodes with only a small amount of difficulty.  But because the results of their resetting would be displayed on the unit, there is still a reasonable degree of tamper-evidence remaining.

False Tamper Indication

On one occasion during my testing, the unit incorrectly displayed a 'Tamper' warning.

This is probably a very rare event, but could potentially occur as a result of the car's voltage dropping too much for too long, especially while starting the car.  So if your unit displays a Tamper warning and your teen maintains they are guiltless, they might be telling the truth.

There's a way of cross-checking this - if the distance traveled reading seems correct, then probably it is a false Tamper message rather than a valid one, but if the distance traveled reading seems way low, then it is a valid Tamper warning.

The manufacturer advises that sometimes it is possible to slightly unseat the battery when first activating the fob/receiver (you remove an insulating strip to 'turn the battery on') and if you think this might be causing false 'Tamper' alerts to appear, you can simply unscrew the battery compartment, reseat the battery, and then screw it back closed again.


The SafeDriver is a very simple unit to install, to understand, and to use.

With a list price of only $69.95 and being available on Amazon for less (currently $56.13) and with no ongoing monthly monitoring fees, it is very affordable.  While it provides only limited monitoring, it is definitely a good value and represents a sensible compromise between 100% realtime monitoring at one extreme and blind trust at the other extreme.

Most of all, it introduces an element of known accountability that may prevent your monitored driver (most likely a teen) from driving poorly in the first place, and surely that is the most desirable outcome of all.


This is Part 2 of a two part review of the Lemur SafeDriver system.

Please click back to part 1 for an explanation of what the SafeDriver is, what it does and how and why.

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Originally published 30 Aug 2010, last update 21 Jul 2020

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.



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