Israeli NGO Shurat Hadin has commissioned the development of a app that allows Android smartphone users to contact their US Senator about the Iran nuclear deal.

http://israellawcenter.org/in-the-media-items/want-to-tell-your-senator-to-oppose-funding-iranian-terror-theres-an-app-for-that/

https://play.google.com/store/apps/details?id=tevel.info.congressiran