Yep, there's an app for that. Often what happens is on 2.4 GHz band that even with good signal, when you get outside there are other wi-fi signals on the same channel from neighbors that will cause problems. Having a phone app that displays all visible networks with signal strength and channel can help determine the best channel. In the US, only 1, 6, and 11 are really usable without overlap.
There are various other sources of interference too - particularly 2.4 GHz cordless phones, microwave ovens, and some wireless baby monitors.