The iPhone is adding another trick to its already impressive repertoire: acting as a hearing aid. The $10 SoundAMP app lets you use the iPhone to enhance the sounds around you.
CNET's Rick Broida spent some time with the SoundAMP:
"All you do is fire up SoundAMP and plug in a pair of earphones. (iPod Touch users will need one with an inline microphone.) Then just raise or lower the oversize slider until you get the volume you wantWhile it doesn't sound like it'll replace more expensive hearing aids, it's there if you need it, and having an app list as varied as a Swiss army knife is one of the iPhone's claim to fame. Beyond just helping our tech-savvy elders, who knows what it could be used for? Bird-watching, maybe, or even spying.
There's even a kind of "audio DVR" feature: you can replay the last 5 or 30 seconds of a conversation just by tapping an onscreen button."