The idea was to seek spots in the city where public web cams are pointed at, and paint QR codes on the ground at those spots (using a template), linking to the camera stream. So when curious passerbys scan the code, they see themselves in a camera stream and feel "watched".
This is what "Oh By Codes"[1] are for.
Instead of trying to paint a QR code, which is difficult, you can just chalk a 6 character code.
Further, you can create them on the fly without using a special tool - just a textarea on a simple webpage.
You can encode up to 4096 characters or a single URL redirect.
[1] https://0x.co