Instructables user stbennett has allowed us to share his project for making a GPS tracked bike lock that could serve as a tracking device for your bike if it was stolen. This cool project uses Arduino and some items you might already have on hand.
Stbennett says, "Having just purchased a half decent bicycle, and living in a city with a bike theft rate almost as high as New York, I wanted to have some peace of mind that if a thief with an angle grinder were to cut through my U-lock I could still catch them.
My main design constraints were as follows:
The device has to be Arduino based so that if I run into trouble I can easily search the forums for help
Whatever I make has to be able to fit into a small bag that goes under my seat
The battery must last for a very long time, at least a few weeks. I don't want to have to plan my bike rides around my lock being charged or not."