The Indoor Dog Restroom.
A friend of mine ordered one of these dog restrooms for her daughter who lives in a high rise condo with a seeing-eye-dog. Since it's difficult for her to take her dog out all the time, this was a great solution for her. From the site: "The mat-and-tray system gives dogs a place to relieve themselves when they can't get outside for respite. Ideal for high-rise dwelling dogs, when owners aren't home, or even just for times of harsh weather, this ingenious system uses a mat made of antimicrobial pourous artificial turf that gives off an organic scent to attract dogs, so they can be taught quickly that it is an acceptable spot for relieving themselves."