They're hard drives sure, but they're also capable of playing video files back in 1080p resolution.
Seagate is probably best known for their hard drives - storage spaces that just sit there waiting for you to do something with them. They're great places to keep your files but they don't do much else.
The new GoFlex Cinema drive changes that up. You can connect it to your TV or projector and play back the files that you've got stored on there. It outputs through HDMI and it gives you a 1080p resolution. If you prefer different outputs for sound you can go with stereo audio or S/PDIF digital optical.
The drive can play pretty much any file you've got. MKV isn't a problem, Divx, Xvid, FLAC are in there as are Dolby Digital and DTS.
It's available in Europe now at around $135 for the single terabyte model, $175 for the 2 TB version and $250 if you want 3TB. No word yet on a US release.