Venues in Osaka, Japan, are being encouraged to post a QR code at the entrance. Patrons scan the code on the way in to show they’ve been there.
If someone tests positive emails are sent out to people who were there with advice on what steps to take next.
On the surface it looks like a neat way of solving the contact tracing problem without burning phone batteries. I’ve no doubt there are going to be privacy concerns, but as a starting point that’s pretty easy to use (photograph QR, job done) it looks like a good one.