Just installed on my C5 the following GPS tracker.
Not overly concerned about security with the large locks/chains recently purchased, (That said, I did have my daily commute bike stolen last week
- it's replacement will also now get a tracker...), but I found this tracker in a local shop at 50% off at about CHF50 (£30). While not technically a fully functional step by step data tracker as it only works only on SMS, but that does mean only a very cheap prepay SIM card is required. It is programmed by SMS and can be activated on demand or if the C5 leaves a set area.
http://www.simvalley.us/gt-170Been testing a few mounting locations over the last days (obviously hidden inside/behind the plastic bodywork):
It seems to work best, in terms of signal and switch on/off reach-ability, behind the rear light (2nd photo). I've mounted it with velco in a small fabric pouch that allows me to get to it easily and if required charge permanently on the 12V battery via a 12V->USB converter.
Just though I'd share in case others have other thoughts or ideas regarding GPS trackers..
Pat