I listened to a three-part documentary about nanotech on BBC radio last month. One of the things that caught my ear was the ability to design programmable nano-machines.

For instance, a bicycle frame could be designed to shift its stiffness back and forth depending on the forces acting upon it from the rider. Imagine sprinting on a bike that can respond to the rider's left-right weight shift at a molecular level. This part of nanotech is not theoretical... it's already been done.