Interesting, but I wonder how profitable these kinds of micro-services will end up being. Seems like the margins must be pretty low, and I'm not sure what unique value you could deliver that a company couldn't more easily extract directly (by buying their own sensors, for example).

I've seen translation offered as another use-case of 21, but that seems like another mechanical turk kind of operation where there really isn't much added value outside of the low fee costs of using BTC as a currency.