Previous owner of our house put a cat door in the wall between the house and garage and built a "cabinet" on the other side with the cat litter box in it. Results were mixed, but at least it wasn't in the house, and most of the problems I think were due to poor construction and lack of planning. I ripped it out after one of our male cats made it clear he wasn't even trying to aim, but my wife then took over a whole bathroom that I kind of miss having, so I am giving some thought to "doing it right".
We live in an area where outside cats last about 6 months on average, traffic, other cats and owls, coyotes, a real snowball IV type place so outside is not an option.
Heart of the thing would be a LitterMaid self cleaning box. http://www.amazon.com/LitterMaid-LME9000-Advanced-Automatic-Self-Cleaning/dp/B000H6AK7A/ref=pd_bbs_sr_4?ie=UTF8&s=home-garden&qid=1196367068&sr=8-4
And some kind of convenient to clean enclosure, as in count the cats, lock the cat door from inside the house, and hose it out from time to time, as well as routine adding litter and bagging the waste. Power would be required for the LitterMaid AC adapter, and an exhaust fan of some kind.
We live in an area where outside cats last about 6 months on average, traffic, other cats and owls, coyotes, a real snowball IV type place so outside is not an option.
Heart of the thing would be a LitterMaid self cleaning box. http://www.amazon.com/LitterMaid-LME9000-Advanced-Automatic-Self-Cleaning/dp/B000H6AK7A/ref=pd_bbs_sr_4?ie=UTF8&s=home-garden&qid=1196367068&sr=8-4
And some kind of convenient to clean enclosure, as in count the cats, lock the cat door from inside the house, and hose it out from time to time, as well as routine adding litter and bagging the waste. Power would be required for the LitterMaid AC adapter, and an exhaust fan of some kind.

.
