On: Show HN: I built an app to use a QR code as my doorbell

[axelthegerman]

I'm not sure what all of this has to do with the OP?

The way I understood the submission is that if you don't have a doorbell - or especially a smart one - scanning the qr code replaces pressing the button.

Others have mentioned that it would be easy enough to copy it and circulate elsewhere but while that's a big issue in my books I don't see the link to captive portals, student attendance etc.

[EGreg → axelthegerman]

I started by addressing the OP and the issue of replaying the QR code directly.

And then I branched out into related issues of proving presence somewhere — online or offline.