I've downloaded it
I think the code is open, isn't it, so that people can look at it and find out that it's not doing anything dodgy
It doesn't take your data. It can't track you. It only knows if you've been in contact with another phone long enough, so that if the other phone enters a positive code, you get notified. There's a points system regarding how close you've been and for how long, and only if it gets above a certain level, does it notify you. That's better than the manual tracking of names that some restaurants do that only takes entry times and not exit times, so they have no idea whether you've overlapped at all.
It's a decentralised system. And enough people seem to have seen the code to know that it's not storing anything or doing anything other than what it says.
It's a shame it doesn't work with older phones. I thought that was a physical hardware problem, though, to do with the bluetooth on those phones - possibly not something they govt can do anything about. If that's what the apple/google api uses, then they've got to work with that.
It hasn't so far drained my battery at all. I haven't even noticed the slightest difference, though my phone is fairly new. Older phones might notice more.