There are new ways of recording content for re-watching it later. You could get a DVR, but a lot of people are going into the HDD route.
What you are seeing on the back of this TV is a MiniStation, and it is designed to hold an HDD to the back of the TV to make it easy for the user to hook it up.
It is a pretty good idea, provided you have the proper cables. It has 500GB of storage and usable as a PC HDD. I am not certain whether or not it is feasible to put it in back, as it is hard to get to, at least in my home theater setup.
The MiniStation is from Buffalo, and will be on sale in Japan for a price of $113.