Got a Tracker Horizon on my X3 - GPS and 'lo-jack' tracking.

Makes no odds if you have your keys stolen or not - you just contact a) Tracker to report it and they monitor its location until b) you report it to the Police and get a Crime Reference Number. On receipt of this number, Tracker activate the 'lo-jack' active side which is then picked up by Traffic Police, Police Helo's and some 'panda' cars (with the equipment in).

If it goes anywhere near a ferry port, they have the kit too and will stop any car that is 'transponding' a lo-jack ID.

The only delay is you noticing the car has gone (unless they have towed it) and phoning it in. If they tow it or lift it onto a flatbed, you get a call from Tracker.

They claim to have recovered every vehicle to date...

Mine was a no-brainer as it was already fitted to the car (at BMW) when I bought it! But after doing comparisons, I would still have gone with them as other systems use the phone network to activate/locate, Tracker has it's own VHF radio network...