5Dmk2, Extreme CF Adapter, Eye-Fi X2 and iPad2 - Awesome Combo!
Now don't get this confused with tethered shooting, rather it allows you to review your shots about 5-10 seconds later on a larger screen like a computer. However it does mean you needed to bring a laptop along or more equipment to really see the benefits.
Eye-Fi also has an iPhone app which was intriguing in application. I only have an iPhone 3Gs so it's not going to give me better resolution like the iPhone 4, but the pairing is very handy for getting images off the camera immediately and on to your phone. If you're a news photographer, this could get your images uploaded immediately to a sharing site (like picassa, flickr, etc...) within minutes. I found that with the file sizes of the 5Dmk2, that I needed to use RAW + small JPG files to expedite transfers. However since I'm not a journalist I found really little application other than the gimmick of it all.
So the next evolution in my hands was to install the Eye-fi app to the iPad2. That's where the lightbulb went off and it was what was missing to really make this combination work well. With the compact size of the iPad2, this gives such a great previewing tool on location. No need for a laptop or other expensive tethering solutions. Immediate reviewing with your clients or models and reshoot as necessary.
The resolution and the download time is very quick so if you have a new iPad2 and looking for something to pair up the two technologies, then this adapter and Eye-fi combo is a nice way to go.
There are several sellers on Ebay that sell these and here's a link to one seller on Amazon.