Comment Tracking on the cheap (Score 4, Informative) 296
Find a Xexun TK-102 on ebay, they will report back their position via the mobile network (you supply a SIM card, and can send it a request for the current position, it will text you back). You can get large extended battery packs too, or you could wire it into the bike's power. They work well enough for us to track drivers at work. Just make sure you get a genuine Xexun one, the others are less reliable and tend to lie about their position, in my case being offset by about 4 miles.
There are separate car sized ones, but I have not used them.