Phones as game controllers

The game I am working on is a local multi-player party game for up to 16 players. However not many people have 16 controllers connected to their PC. So I was thinking about using phones as additional controllers.

I can think of a couple of different ways to do this:

This seems such a simple, useful re-usable project that I would expect it has been done before. Does anyone know? If not, is anyone interested in working on it? It might make a nice little project for a student.