Remember Airfoil? Quick refresher: it's a third-party piece of software designed to complement (or improve upon) Apple's Airplay service. Last year we wrote a guide on Airfoil, explaining how to stream audio from any Mac or PC app to an Airplay device using Airfoil. Version 3.0 of Airfoil's companion app for iOS, Airfoil Speakers Touch, just hit on Wednesday. The app developers at Rogue Amoeba have added in the ability to turn any iOS device into an Airplay receiver.
What's the point? Well, with the free iOS app and a $2.99 in-app purchase, you can stream Airplay audio to an iOS device without paying for (or using) Airfoil's $25 desktop software. You can stream audio from an iPhone to an iPad or from a Mac with iTunes to any mobile device using Airplay.
Airplay-compatible music players are more expensive than plain old speaker docks, which makes the combination of an iDevice and a cheap dock a money-saver. If you're not already paying for iTunes Match, Airfoil is a convenient way to stream your library to your phone or tablet without spending $25, though you obviously don't get the cloud backup.