So many people have stories of their bikes being stolen.
I've recently come across this device :
http://www.integratedtrackers.com/GPSTrack/
If your bike gets stolen you get sent an automatic text, and you can then follow the path the stolen bike is taking, on your computer.
You'd probably then need to get the police involved to accompany you when you go to get it back.
I believe the police sometimes use 'bait bikes' fitted with devices like this. I wish they'd do it more often. Sometimes they get led to a whole stash of stolen bikes.
At £83 for the SpyBike and no subscription fees, that seems reasonable for the satisfaction of catching the thief.
Steve