I continue to be astonished by all the different ways the iPhone is being used, including as an extension of your senses. I've already written about the Eye Glasses app ($2.99), which lets you use your iPhone to magnify small print. And you can also use your iPhone as a hearing aid. SoundAMP ($9.99) is an app that uses your iPhone to amplify ambient sound. Your iPhone picks up the sound via the built-in microphone or via a microphone on an external headset. And in both cases you listen to the amplified sound via earbuds or the headset. A couple of the reviews suggest that the combination of microphone and earbuds works the best, but that's very anecdotal. This app was recently selected by technology writer David Pogue as one of the top medical apps.