German "Future Store" lets you grocery shop with your cellphone - Engadget
I thought abut one idea, just let users pick their grocery items online, mark the time they want it, even mark some items as repeat or favorite with desirable price etc. Then they can either pick it up from store or let the store deliver it weekly(or by the store delivery schedule like mail or garbage schedule). So that the store doesn't have to stock as much and people can save gas.