As a DC-area resident, I've been one of many local developers saying that the DC Metro needs some sort of API. If anything, just to be able to build or integrate transit routes into existing apps. The wait appears over and the Washington Metropolitan Area Transit Authority now has an API.
Flight price tracker Yapta's value proposition sounds a bit like Robin Hood of the travel industry. It will not only track travel prices for you, but to help you get a refund should the price of your reservation fall after you’ve booked it. I wouldn’t be surprised if Yapta can also be used to retrieve kittens from high branches, but that part of the Yapta API isn’t documented yet.