I would love to use my iPad as a tethering device for instant review but I can't see how to set it up.
I have a nasty suspicion that it's not possible.
Please tell me that I'm wrong!
You could use an Eye-Fi Pro Card and an Application on the iPad (or iPhone or Andriod phone or laptop ect.) to read it.
I have not used this approach myself so I cannot say if it is any good however it might do what you want.
There is a description here that shows how you can do this, but it seems a bit of a convoluted solution. I don't there is (currently) anything that allows you to link an iPad to a WiFi enabled DSLR directly. But I certainly wouldn't rule it out from ever happening.
There was an episode of TWIP that discussed an iPad Camera Connection Kit. TWiP Episode #166