I think this kind of thing has been tried many times. Even I made one several years ago, mainly as a way to try out a few different cross-platform tools.<p>The difficulty is not implementing it, it&#x27;s getting a critical mass of people to start using it. It&#x27;s hard enough to get anyone to try <i>any</i> app these days, and you are up against that difficulty squared: multiple people geographically close to each other must all be using the app at roughly the same time, or they will just try it once, say &quot;nobody on it&quot; and forget it.<p>If I were desperate to get traction for something like this I would focus on one spot with lots of potential adopters, maybe a school or college campus, and come up with a way to get lots of users there onboard, fast. Then you might get to a critical mass which can sustain interest and maybe even expand, like Facebook did starting from Harvard, then expanding to other colleges and high schools, and finally letting in everybody and their dog.