About contact tracing apps, I'm skeptical they are so effective. For example: "iPhone users are asked to keep the app open so it can keep using Bluetooth, which iOS will otherwise throttle to save battery life." How many would actually do that?
Wearing masks is clearly more important, and lacks the privacy risks, and are already cheap and available. I've worked quite a bit with Bluetooth. Its far from reliable, unless users really actively manage the process.