Unfortunately, there is not currently one single perfect app which meets all the needs of a DC transit junkie. This is one of the best, because it lets you type in the NextBus numbers directly, and it includes the Circulator as well. My only gripe is that it wont let you save more than three bus stops. But other than that, this app is pretty comprehensive. I also use myTransit DC and circ@dc.
Radar467 about find a metro dc