We’re suckers for apps that focus on simplicity and usefulness rather than whiz-bang features that look cool in demos but have very little practical utility. Rogue Amoeba’s Airfoil is one of those apps that we couldn’t help but take a liking to right off the bat.
It has a simple goal, performs beautifully, and it’s cross-platform to boot.

The Airport Express is a great portable Wi-Fi base station, but its best feature is the severely underhyped AirTunes, which allows you to hook the Express up to your stereo and stream iTunes audio over your Wi-Fi network. But AirTunes only works with audio from iTunes, which is where Airfoil comes in.

Airfoil's simple interface lets you pick and choose where you want your audio to go.

Airfoil allows you to stream audio from any application—or all the audio on your system—on your Mac or Windows machine via an Airport Express or Apple TV. So now you can stream Internet audio from Pandora—or music in formats that iTunes doesn’t support—directly to your home stereo. If you have multiple units, you can pick and choose which ones to stream to, effectively turning your Mac into a multiroom audio system without the spendy dedicated hardware. Even better, Rogue Amoeba offers free add-ons that will turn any computer, iPhone, or iPod touch into a streaming destination. Adding powered speakers to an old Mac Mini is a great way to repurpose some old gear that’s otherwise just gathering dust. And imagine the possibilities of an iPod touch connected to some portable speakers for no-fuss outdoor tunes at your next pool party.

In our testing, Airfoil performed admirably, sending audio from Web videos and local files to our Airport Express, as well as other computers running Airfoil Speakers, and to our iPhone running the free Airfoil Speakers Touch app. Unfortunately, Airfoil is one-at-a-time affair. You can stream your audio to a combination of speakers, but you can’t stream different sources to each. Airfoil did a good job keeping streams in sync, and if you’re so inclined, there’s also an Airfoil Video Player that will let you watch video on your computer, while sending the audio to your home-theater setup. And while the app is simple enough to get going without reading the manual, a couple of crucial plug-ins that add functionality aren’t fully explained, although they do work as advertised.

Airfoil one-ups iTunes by streaming any audio to any Airport Express, computer, iPhone, or iPod touch on your network, perfect for setting up multiroom audio using gear you already own.

Airfoil
COMPANY: Rogue Amoeba
CONTACT: www.rogueamoeba.com
PRICE: $25
REQUIREMENTS: Mac OS 10.4 or later
Makes AirTunes much more useful. Streams to many kinds of devices. Cross-platform. Universal binary.
Can't send multiple streams. Easy to get started, but documentation of advanced features is skimpy.