No question, just an App that lets people tell congress their point of view

A waste. And this is why: Such an App would be immediately used for automated mass mailing campaigns to congressional offices. Any messages from such a service would be seen as "astroturfing" and discounted out of hand, unless it agreed with the congressperson's existing view.

Just email them.

Given the fact that what most constituents have to say and what they believe has "almost no effect" on what a Congressperson does I'm going to say it would be a waste