well there is
www.connect2car.com
but i don't think that's the solution your lookin for
but i know with some remote start systems they give you an option of adding other sensors
you would probably have to do some reverse engineering
where if you had one of those wireless usb in the area around your car that it would sense that it is you and if you were by the car by about 3 seconds then it would start the car up
probably have it work off a timer to trigger the remote start
it seems like a fusion brain might be able to help with this but then again in order to use the fusion brain the computer has to be one