The issue always comes down to the fact that you want to have X number of touch screens. You really have like three gross level options:
1. You somehow get a single machine to somehow animate all those screens (i.e. no smarts in the screen, since machine driving them all.)
2. You use something like RDP so that you have one machine on the back end, but effectively that machine is running X number of user sessions.
3. You have X smart clients that run their own OS.
#1 would be something like the Rad-IO system (the little 240x160 pixel ones.) You have one machine, and the output from the video is split out and shown on up to 8 screens.
#2 is something like that the UTMA devices, where the devices are just dumb displays and all the actual work is done on the back end on a single machine, by having RDP sessions runnign on the back end. Just using something like an Airpanel as an RDP client would be the same thing basically.
#3 means each client is a separate computer. That could be that you have a computer in each room (and it could be an all-in-one touch screen and computer that's designed for in-wall mounting), or you could put them all in a closet and just run wires to the room for the video/touch interfaces. These two scenarios are exactly the same ('topologically'), they just differ in where the client machines live.
#1 is interesting but there's not really much built in support for such things. The Rad-IO guys really work best if you have a dedicated machine just to run the Rad--IO because you cannot run another video card at the same time. YOu can plug a local display in, but you are limited to the 640x480 resolution of the Rad-IO video. It would be the 'lightest' of all the options, but unless someone comes up with some highly speicalized hardware to support it better, it's kind of limited.
#2 has it's pros and cons. The big con is that you need a fairly mondo sized machine if you want to run a number of clients, because all the work is done on the back end. And if the box is also going to be a media server and automation server, it starts getting kind of iffy. So you may end up with one moderate and one big machine. The performance will not be as good as separate clients but it's probably not bad.
#3 is the most flexible and highest performance. The big downside if you put the machines in each rooms is maintenance. You end up walking around the house to make changes, and the machines are open to abuse potentially by those psycho little bra... I mean the kids. Using a blade server is a way to have this solution while still maintaining a centralized system, so that the only thing exposed in the room is a screen. Everything else is in the closet.
It might not even be the most expensive. If you look at something like LIfeware which uses the in the wall type touch screens, those guys are around $3K a pop. If you wanted to have 8 of those, that would be $24K, before you even bought their product and other accoutrements. You could do a blade server with 8 blades (plus a bigger one for the main server) plus stanard touch screns for a lot less than that I think.
Of course, if you can handle just having a standard PC in each room, that could be inexpensive according to how you go about it. A $700 mini-ITX system could drive a $650 15" touch screen in each room. It's just not as 'clean and profession' as just having a magic touch screen on the wall.