Heads up we've been building a very similar app over at https://www.covid-watch.org/ along with another group named CoEpi (who don't have a website afaik). We're currently abstracting our bluetooth implementation out into a library (for iOS and Android) and hope to release that along with v1 of an open standard for talking to a central server soonish.

The value of this app is fundamentally limited by the network effects, so in my view its best if we gather all the groups together and share a single data store / standard.

let's talk about privacy after people stop getting stockpiled in ICUs because that's a super emergency