A cross between treadmill and climbing wall. It is made up of a series of panels approximately six inches high attached to a belt. The top of the machine is pivoted, allowing for adjustment of speed and angle. Hand- and footholds are strategically bolted onto the panels. Several courses of varying difficulty are made by using different colored grips for the courses, and leaving the climber to only use the appropriate colors for their chosen course.
The whole machine stands about 9 feet tall, and as such can be safely operated without belaying. This also lets people who suffer from acrophobia enjoy climbing. Its main weakness is boredom due to its smallness.
Sources: personal experience. At time of w/u, Brewer's Ledge is selling them through www.treadwall.com.