If you've travelled abroad, perhaps you noticed that different denomination bills had different physical sizes, a design intended to allow people - especially the blind and visually impaired - to distinguish how much a bill was worth just by touching it. American currency has not followed this lead!
LookTel Money Reader seeks to solve the problem via smartphone: Just fire up the app and point the camera at any bill - $US1 up to $US100 - and it'll announce what denomination it is aloud. From the demo above, it seems to be snappy enough for someone who's visually impaired to rely on when they're out and about, and its ability to read off bills as they're folded from a wad is particularly impressive. $2.49. [iTunes via NYT]