Recently, a study in the University of California showed how to create a demodulator using nanotubes. So far there were advances in memory containers such as this and that and also batteries but all of them, as Sunny remembers, trying to build small structures following the design of big things.
Quantum computation nowadays have exactly the same problem, quantum effects in a classic assembly, big, clumsy and very expensive. If it was required a quantum effect (the transistor) to make classical computational cheap and available what will be required to make quantum computers cheap? A SuperString effect? Something messing around with the Calabi–Yau shape of the 6 additional dimensions?
Anyway, back to nanotech, building a nano-battery is cool but using ATPs as the primary source for energy would be much cooler! Using the available nano-gears and nanotubes to make a machine is also cool but creating a single 2,3 Turing machine (recently proven to be universal) would be way better!
Once you have the extremely simple processor like that, a nano-modem, some storage and ATP as food you can do whatever you want for how long you like inside any living being on Earth. Add a few gears to make a propeller and you’re mobile! 😉
Of course it’s not that simple, but most of the time to state that something is viable means exactly the same as to say that it’s classic as in boring and clumsy and expensive and brute force… well, you got the idea…