QFC, the grocery store closest to me, has those irritating shoppers cards. They try to motivate me to use it with discounts, but that just makes me want to use a card, I don't care whose card and I don't care if the data is accurate. They should let me have my data or make it useful to me so that I actually care.
I can imagine several useful tools based on this: automatic grocery lists, recipes using the food you purchased, cheaper alternatives to your purchases, other things you might like based on what you purchased, or integration with dieting websites or software. At any rate, right now all I care about is getting the discount from using a card, but if they made the data available to me then the grocery store could align our interests and I'd want to ensure the data's accuracy.
I like the idea of QR codes, encoding URLs and placing them on real world objects, but the QR codes themselves are kind of ugly. To make them less obvious I thought I could spray QR codes on to an object with an infrared reflective paint and shine infrared light on the QR codes, since most cameras, for instance the camera in my G1 phone, pick up infrared that our eyes do not.
In looking for this paint I've found that it comes up a lot in relation to the military for things like paint markers that are visible at night with proper equipment, and paint that absorbs IR light to make vehicles less obvious to night vision goggles. Even though the first reflects infrared light and the second absorbs it websites end up refering to both as infrared paint which made it difficult to search.
Additionally I found links to some other geeky infrared projects:
At the grocery store the other day Sarah and I attempted to find shallot for a recipe, but I can't tell the difference between shallot, sweet onions, yellow onions, etc. etc. We found something that we decided was the closest we'd find in the store and I believe we picked correctly because at checkout the cashier rang it up as shallot.
I think this could be a practical problem that the 20q Pocket Mind Reader should be able to solve: obtain the name of an unidentified object. When we got home I decided to test the 20q Pocket Mind Reader on shallot. Unfortunately, it told me I had an onion, but I think if these were designed for identifying unknown objects based solely on information you can obtain by looking at it, rather than requiring knowledge of seeds, where it grows, etc. it would do better. Or I could just ask someone who works at the grocery store.