With my jazzy new mountain bike, everything is designed to come apart in seconds for adjustment and everything can be stolen just as quickly, so I wander about carrying a seatpoest and seat, and have a fifteen pound chain that weighs almost as much as the bike. EC thought about this and came up with such a clever solution: the seat post connects to the handlebars to turn the entire bike into a U-lock. He puts locking nuts on the hubs and voila! a self-locking bike.
One sees so many bikes that look like this- a good heavy cable lock and still the bike is stripped.
EC also has an idea for integrating a pump into the seat and tubing inside the frame to the tires, but that is perhaps overkill. and how can the seat both be a pump and a lock at the same time? I would stick with the locking idea. ::ECSketch via ::Core77