GSM Trackers - Any good?

[jimxms]

I'm looking at one of these as a cheap way of protecting my car:

http://www.ebay.co.uk/itm/NEW-GPS-car-tracker-remo...

The main selling point for me is the ability to cut the power/fuel to the car by sending it an SMS message. I think this would be particularly handy if you were forced to hand over the car keys or there was a short time between the car being stolen and you noticing it missing.

Does anyone have experience of how well they work?

[jimxms]

Guessing that's a no then