Bought a cheap tk102 based tracker from ebay - fits in my obd port. It did come with some software that allows for some higher functions (ie obd data to be transmitted also, but it didn't seem to do much, and I preferred a web service based tool).
Had a look at traccar and got that set up on a linux machine at home, seems ok Does lack geofencing and alerting, which is something I'm keen on.
So may look at opengts - apparently traccar can talk to it (updates the db directly).
Seems a bit of a giggle. I like the idea of setting geofenced locations. Basically want to know where the car is for unauthorised use, and currently when I take a long drive I track it via my phone, so I'd be able to do this via the site also.