Android / IPhone Bar Scanning System

I am looking to set up a app that will scan Qr generated bar codes, and liase with a database on the internet to confirm the qr generated ticket is genuine. It will work like this, Customer presents their ticket that was sent to them by email, we scan with a smart phone say android, information comes up on screen of what bar codes says app checks with company database that ticket is correct screen displays confirmed. we have not yet decided on android or iphone smart phones so this project is currently open to both.