IDEA Create an app that allows you to scan bar codes while shopping, to allow for you to automatically check of things on your shopping list.
Pain Why do I need to think about what I have to go shopping for, when I can have computers tell me what I usually shop for.
Gain in a couple of months you will be able to have an automatic shopping list, due to the things that you've already registered.
Making money By aggregating the data you(the developer/businessman/whatnot) can sell it as large-scale consumer statistics(I think scientific use), or maybe even(if morale allows) use it to effectively do personal targeting!
Challenges
- Bar codes -> product match (Try googeling "57045399") - possible solution(http://www.upcdatabase.com/itemform.asp)
Isn't this already built into modern fridges?