Re:Phone application for restaurant customers
Our credit card processor Square already has such an App, it is called Card Case, and allows our food cart customers to order and pay off the menu on their phone. It is free, all I have to do is keep my menu updated in my payments app, and it can be used at any restaurant that uses square for payments.
Not to rain on your parade, but POS integration is no simple matter. Look how many establishment still use a separate payments Verifone or Ingenico terminal. Plus there is the tip issue, waitress banks, advertising and promoting the app, PCI compliance, printed receipts...etc. Many smaller restaurants use a casio or other dumbPOS from costco, the larger ones use several vendors - halo, micros, squirrel, all with different integration issues. Selling the app is problematicc too. Calling on individual owners is expensive as you have to go to lots of locations, and they are usually broke and have high support costs. The larger chains/franchises are going to be a long sell, you have to sell the IT staff, the store mangement, senior management and the franchisees.
Good luck, I'm much happier flipping crepes and doing websites than being in that world anymore.