I use a Spybike (http://www.spybike.com/ http://www.spybike.com/) Unfortunately, the company seems to have gone bust. They have stopped responding to emails -

I use a Spybike (http://www.spybike.com/ http://www.spybike.com/) Unfortunately, the company seems to have gone bust. They have stopped responding to emails - and their tracker is 3G only - many countries have started to shut down their 3G GSM trackers. There was one on Kickstarter before called the "Bike Spike" - however, it turned out to be a fraud, and the creators ran away with backer's money (I didn't back them). The Spybike isn't bad - the big issue is getting a GPS lock in urban areas, long GPS lock times from a cold-start, and battery life. Definitely keen to see what else people are suggesting these days.