With this new product from PLC Electronic Solutions, you can have wireless control of your lenses with your iPhone or iPad. As it turns out, this isn't just for your Canon EOS 5D Mark II (reviews) or Canon EOS 7D (reviews), you can use it on just about any video camera. Their product is called the fSTOP wireless controller and is set to retail for $1,389 (US).
UPDATE: I thought I'd also remind everyone of the other entry in this remote follow focus arena – Redrock Micro's mRemote that was announced at NAB (disclaimer – yes, Redrock Micro is a planet5D advertiser but that's not why I'm putting it in – I thought it important that if you're reading about the fSTOP wireless that you might want to know of the others in the field that you may have missed).
This is a good overview of what the device is capable of doing and how you set it up:
Here's the device doing follow focus on the 5D2:
Here's a sample showing the iPad:
(Photo credit: snap from the video)