Well I think I'm gonna attempt this one since its the cheapest "instant" tracker. A lot better than guessing were your bike was taken to.
http://www.opengpstracker.org/
You text the prepaid phone and it text back to you all the info. You just have to get pay cards for the texting but thats a small price to pay when you get a chance to bust down the door to the chop shop and cap everyone.
Just would need to volt reg it to hook up to the moto battery.