Amazon has released Price Check, a free app that allows you to do some comparison shopping. You start by saying the name of your target product, scanning its barcode, typing its name, or snapping a photo. You'll get several results; tap one to see who's offering it with prices and shipping costs listed. Of course, Amazon hopes it has the lowest price, but it doesn't always win.

I tried the app in a local store and found the barcode scanning and voice recognition worked well. I took a picture of some DVDs, and the app figured out what the movie was and offered meaningful price comparisons to other retailers.