37 Coins

Send and receive bitcoin via SMS.

I've heard that SMS is used quite a lot in developing countries to exchange money between people. Will be interesting to see if something like 37 Coins will helps to proliferate bitcoin and other crypto currencies that have low transaction fees.
Liquidity is key for BTC to take off (and frankly BTC taking off is going to help blockchain-based businesses in a huge way). And liquidity means merchants or access to fiat currency, so on its own it isn't a game changer, but by creating an attractive application layer for consumers, maybe growth can bring the rest of the ecosystem along.