[lancewiggs]

http://Taggle.com.au (I'm an investor) has a small device that allows remote tracking of assets like bicycles for years without an external power supply. The tiny devices broadcast a low powered wide spectrum ping every 20 mins to 1 hour and very smart receivers triangulate to provide coordinates. The transmitters can also send data, generally a meter reading or if a secure element is broken.

Taggle Systems are focussing first on remote reading of water meters and other water utility use cases, but once networks are in place then tracking bikes will be doable.