This version of petnames is too complicated. You can't get a good petname system without getting rid of broken crap first. Scanning a QR code on a flyer should be the sole introduction point and just lead to a secure communication from then on. Why do I want petnames for phone numbers or other insecure things?
To put it differently, no petname system built on top of unix / web crap will ever be good. Everyone (like posters here) will not understand what they're doing and just write code that breaks it on all layers of the OS and GUIs. Guaranteed if Android starts using petnames more there will just be issues like it copies someone's petnames all over yours, shares the ones you didn't want to share, etc.