I haven't got a model A yet but I was tempted to get one to see if it could run as a simple orbiter combined with the small adafruit touchscreen and placed in a wall box to control lights, set alarm status etc.
Not sure if the 256mb ram would run orbiter though but a web interface may work, I know this could be done with the model b but this a+ is quite a bit smaller now and more importantly in-wall its not as tall.
Just my ideas there so cheep you can afford to experiment:)
Don't know much about the A+ PIs but it seems to me that if you're looking for a wall-mount orbiter, you can get a cheap 7" android tablet for just a few dollars more. I guess if you particularly want it to be small and extremely low power then the PI is a good option but if it's a price-point thing, to me an existing tablet would make more sense. And it has the added advantage of being able to run Qorbiter and do other stuff if you want as well - I have a $73 tablet that is wall mounted. It runs touch-orbiter but I use it primarily as a permanent IP camera viewer for my gate camera. It has been running for about a year and a half now as smooth as you like and the screen is on pretty much all day.
On occasion I take it off the wall (magnetic mount) and the children play games on it or I use it for the odd e-mail, to control my media, or I move it to the entertainment area if we're entertaining and expecting guests so I can keep an eye on the gate.
My only gripe is power- I have an ugly cable running to it from the power supply.