I am trying to find a solution for this, the best way to get cash paper money for your bitcoins. Not every country or city has bitcoin atm to get cash instantly for your bitcoins.
I have one idea in my mind "an mobile app shows nearby money holders, you deposit btc to your account and click on any money holder nearby, now he gets notification and your bitcoin goes to escrow (also he can see the). You will generate a QR code you have to share this code with him until he gives you cash, you can go to him to pickup or ask him to come at my place. Once you let him scan QR code from your mobile phone the btc goes to his account."
What do you think?
Your idea is nice but i see there are few things that may arise problem in future;
1. There is local bitcoin which is also compatible with mobile so people may not get interested in downloading whole new app to do this.
2. you also have to concern about securing all the bitcoin that get deposited, if there will be some hole in your security you will loss all hard earned trust.
3. Walking to that people or asking him to come to your place with cash in hand to just scan your private key (qr code) to get those bitcoin may become tedious job for buyer.
People really get scared about downloading new app and storing/trusting app with their bitcoin. They may just use paxful, localbitcoin like site which also have inbuilt escrow feature.