GPS Tracking for Stolen Bikes

Hi, we now have an integrated tracker that fits in the bicycle stem called Spybike which is cheaper than Spylamp (GBP80 + VAT). Still working on reducing the prices...I am wondering, would people prefer to pay full price upfront and then find their own SIM card. Or buy the tracker for cheaper (say GBP40) and pay a monthly fee. ie 3-4 pounds per month for SIM+tracking? We are looking at offering both models
www.integratedtrackers.com

I like the idea, but the SpyBike is out of the question for those using a quill stem.

I also think that the SpyLamp is a bit dodgy. The thief might just remove the light for one reason or another.

Why not release a unit as a standalone? That way people can put it wherever they like and in a manner that will suit their bike. I'd probably just tape it under my saddle with some black electrical tape and make it look really low key. Or maybe find a way of fixing it into the seat tube.