You are shopping. You just took a snap of 'Barcode' of the stuff you are about to buy. And your phone just told you "Hey this stuff is more cheaper at the other shop nearby". or "Hey don't buy that stuff, this comes from some controversial manufacturer!".
Yes!... this is possible with Advanced User Resource Annotation or AURA a free application from Microsoft Research, which though is in early stages but will give you a taste of the future.
Depending on your mobile phone it might require a Lens-kit... you can get that also by just sending a Self addressed stamped envelope to MSR.