Philips has started selling on the Apple App Store the Hue Light Bulbs which can be controlled on your iPhone and iPad. The light bulbs operate on the open zigbee standard with a starting price of $199 and comes with the wireless bridge and 3 LED bulbs. Additional bulbs can be had for $59/bulb. The wireless bridge in the starter pack will support up to 50 LED bulbs.
Here is more info about the bridge from the Hue website:
The hue bridge is where all the clever stuff happens. It’s the ‘bridge’ between your bulbs and your smart phone app. And it can link up to 50 bulbs at a time. To connect your bridge, first power up and then plug into the back of your wireless router, using the network cables provided. The blue lights go on one by one. When all four lights stay on continuously, you’re ready for action.