It would require only the development of an internet-connected and ethereum-capable bike lock (potentially including GPS) to create a crowd-sourced by-the-hour bike rental system.
Riders could pay a small fee and a larger collateral. In exchange the bike lock would unlock for a period of time. When they locked the bike lock again, they could be refunded their collateral, less any "fines" for keeping it past its "due date." A portion could be reserved until the next rider attempted to use the bike. If this rider finds it in the correct place, and in working order, the previous rider would be be fined further. This would create incentive for the bike's owner to keep it well-maintained, as riders would be unwilling to take on this risk if it appeared that the bike was a few miles away from a popped tire or chain breakage.
If the cost of this special lock could be kept relatively small, with both the hardware and software sufficiently robust, we could have a boom of ordinary people dusting off the bikes in their garages as an investment.
What problems do you foresee in such a plan, beyond the obvious risk of the development capital for the device itself?