The AT&T U-Verse device is one that doesn't need to be hooked to a cable jack to work as it works over wifi. However you do still have to hook up the HDMI to the TV.
Now if it has a RF remote like a lot, but not all providers have for their service, at the very least most offer options with an IR extender.
You could get away with having power behind the tv and just using some industrial strength velcro and sticking the cable box to the back of the tv and just hiding the wires behind the tv. I have done that for friends of mine before who wanted a very clean install.
The Chromecast device looks like it would do all your blueray player would do, well you know, except playing bluerays. That looks like something I would do, since it's brought up, I may snag one for myself soon.
I was looking for a better option than using my 360 and paying for Gold just to use the streaming features since I don't do online gaming anymore.
The setup I currently have is a 55" LG LCD on the wall above my fireplace. I then have a vertical entertainment center to the side of the fireplace, this houses my cable box, game systems, power strip, router, etc, as well as obviously movie and game storage.
I have the HDMI cables and the power cord running horizontally into the back of the entertainment center. You can barely see the wires since it is such a short run. I think there is about 12-18" between the edge of the TV and the entertainment center.
I have thought about covering it with some of that wire concealer strip, and have also played around with the idea of installing a power outlet behind the TV and using really long HDMI cables to go from behind the tv, up into the attic, and down to behind the entertainment center. The cost of long HDMI cables is what is keeping me on the fence from this, but it is definitely an option for installs like this.
If you did want to do a setup like in a closet, you can definitely do that. Fishing wire isn't all that hard if you have the right tools and enough cable. The HDMI cabling will definitely be the spendy part of the project depending on distance. Also if you do that, make sure to get and run wire for an IR extender. They have ones you mount in the wall next to the TV and relay the signal to a unit that directs the signal to whatever device you put the sending units on.
This is actually my line of work doing this stuff, so feel free to ask any more detailed, specific questions.
BTW: In theory, the wireless HDMI sending units work, in practice they aren't that great. Also I think for his application, it wouldn't help and have him in the same scenario since he would need power to the HDMI receiever and HDMI from there to the TV. The wireless box from at&t would do the same thing, but without the middleman.