I have had cobratrak fitted wth a previous car. Worked really well, had some nice options to follow the car all the time and this made trips a bit more fun as you could see where you had been online. The system also ha a feature where if the car was moved without correct ignition start it would notify the police and the owner of the car, apparantly, never needed it.
You could log into the website and see the basic information from the car such as the speed, directin, rev counter ad a few other items on the car. If you want a laugh, enable the logging before you hand the car in for a service. You cnat or at least couldnt leave the system always transmitting as you got a limited number of texts from the system, so not something you could leave always on updating the website.
You can check ad-hoc any time you want and enable the logging as you wish, lso it activates if it detects the cars is being stolen.
The dowsides are the really small reduction in the insurance ( for an A5 worth about 37k) really didnt make much difference for my insurance costs. I guess this might depend on the area you live though. There was also an annual subscription to keep the system live.
Overall I think it works, but it didnt reduce my insurance by nearly eneough to justfy the extra cost, even the annual subscription was more than the reduced costs. Dont know if this as also because I have the car locked in a garage and live in an area thats pretty low risk. Touch wood etc etc
I never stuck the stickers on the car advertising it was fitted, some would say its a deterent, others would say it lets people know they need to fnd the device (which isnt supposed to be easy) and disable it.