Another possibility is the Garmin Astro dog tracking device. Transmission range is line-of-site so in the urban environment a bike is most likely to be stolen, it may not provide the range you want.
Originally Posted by dmac49
What is needed is something that immediatly alerts you when your bike starts moving a few feet. I note that the Garmin Astro might provide a way of doing this:
Switch over to the Dog Tracker page to view a compass pointing to your dog’s location as well as his current status: whether he’s running, sitting, on point or treeing quarry. Astro can also sound an alarm to let you know instantly when your dog goes on point.It is unclear exacty how this function works. You should be able to download the manual and find out. Maybe it is a sensor that attaches to the dog's leg that detects when he points. On a bike, perhaps this could be attached to your kickstand so that if the kickstand is raised, your bike goes "on point" and you are immediately notified.
Update: I read the manual and it is still unclear what triggers the "on point" alert. It does not seem to use a sensor outside the collar unit. Perhaps it just works off no movement for a certain elapsed time. Thus it seems you could not use the "on point" alarm to detect if your bike's kickstand went up or if moved from its parking spot.