, a feature that debuted with Apple’s iOS 4.2 and iTunes 10.1 updates, lets you stream music wirelessly—over your local Wi-Fi network—from your Mac or iOS device to compatible speaker and home-entertainment systems. The feature has been available since November, but aside from Apple's own and units, systems that take advantage of AirPlay have been slow to emerge.

Harman International jumped into the market on Monday morning, providing a —a circular desktop speaker system—to fans of , but provided no information on pricing and availability other than "Available this spring."

Still, the promise of an AirPlay-compatible product is a step further than many manufacturers have gone. Here's a quick look at the state of AirPlay products: what's actually on the market, what's coming, and what might be on the horizon.

: appears to have earned the distinction of First To Ship, as the company hit the market early with its , an AirPlay-enabled version of the . The $600 audio system features five individually powered drivers for high-quality sound; it also sports a traditional dock-connector cradle for iPhones and iPods, as well as a USB connection for grabbing digital audio from a computer. The Zeppelin Air is available for purchase through the .