Have you ever used the WalletZero app? It takes your various discount/frequent shopper cards and stores their barcodes on your phone. I call it up and the check out clerk scans it in. No need to carry those plastic cards anymore. It's supposed to work for my gym as well, but they want a photo ID, so it's not enough to just have the code.

I wonder if this would work for things like concert and sporting events. Yankee Stadium scans my ticket barcode to let me in. Why couldn't they scan my phone screen? Think of all the paper that would save – no more tickets!