I've been using the Seagate GoFlex Satellite since it came out.
Excellent solution, specifically for what you want to do.
Seagate Satellite Wireless | Seagate
There's no app for Win8 yet. But the drive puts out its own WiFi signal, and you can access the movies in full HD wirelessly via your browser, or your tablet's media player. Or of course you can hook it up via USB 3.0 too, but that would only be for situations in which you did not want to go wireless, like on a plane.
The video quality of this unit is amazing. Beautiful HD. Of course, I use only very high quality files, so my movies are usually 7-11 GB in size. But you will not be disappointed.
Nice! Now I wish I hadn't bought the 64 GB expansion card. A 32GB card would have worked and I could have used this for everything else, since it is mobile. I like this a lot actually. How long does it take to charge up (I see on the page you linked it has a charge of 7 hours or so). Good thing is that one can load media plus documents, which is cool - like an AIO unit.
Edit: How does it work with Win 8? The system requirements say upto Win 7. Also, based on what you posted, this means that I could stream my media files and play them using any of the media apps available for RT (as long as they are capable of playing the file)? Thanks.
Edit 2: I was just reading a user-review of this and it was pointed out that "due to the way the wifi connection works, you're either connected to the device or you're connected to your Internet connection - you can't be connected to both at the same time..." Is this true?
Is the wireless plus from seagate the new satellite? Seems to have the same features, with a bigger driver and longer battery. Updated model perhaps?
Wireless Hard Drive, iPad Hard Drive | Seagate