Problem with the Sling Box is that the connection you have overseas may not be good enough.

I would be happy if you can just transfer the recordings on your DVR to the iPad so that you can view them later, even on a plane where you won't have network connections.

Obviously apps. like Air Video and Zumocast can transcode media on your computer. Now it's a matter of the satellite and cable companies giving you access to the keys to decrypt these recordings.

Dish is offering some kind of integration with Sling which they bought. Direct TV is said to be working on something called a Nomad but it's not clear they will work with iPad so much as their own proprietary device.

Comcast is advertising some kind of app. as well.

You can only hope that as iPad and other tablets become more popular, these TV providers will rush to support them, though with all kinds of limitations.

Presumably HBO will find a way to offer their programming somehow as well.

They will probably limit to streaming, since if you have the content stored locally, you have no need to buy DVDs or digital downloads or whatever.