Apple's AirPlay is great for sending music and video from your computer to other devices, but not so great at sending that media to your computer. AirServer changes that.
AirServer is a piece of software that will let you send music and video from your iPhone/iPad to your computer. This is good for people who have nice speakers hooked up to their computer and want to play music from one of their mobile devices on it. A little specialized, maybe, but a godsend for folks who've been clamoring for it.