Today, for the first time ever, Amazon Go opens to the public, and it's pretty much already cementing itself as the store of the future. It's actually said to almost seem like a subway station, with gates blocking the entrance that you walk through to enter the store -- which is only allowed if you have the Amazon app.
Basically, you scan your app as you walk through the gate, pick what you want from what's available in the store, and walk out -- your Amazon account gets automatically charged. There's no registers or cashiers to wait on you or anything.