The hardware consists of two parts: a display unit that's posted outside of each conference room, and a controller unit that's located in Rapleaf's wiring closet. The display unit shows the current and upcoming reservations and an LED status indicator that can tell you from a distance whether a room is good to grab. It also has a pair of buttons - one to make an ad-hoc reservation and one to cancel the current reservation. The controller unit interfaces with all the displays to distribute power and data, both of which run over a single standard Cat5e cable. Both the controller and the displays are Arduino-based.
The software component is a Rails web site that allows for configuration and integrates with Google Calendar. Reservations made via Google Calendar are sync'd with the Roominator, and vice-versa. The controller unit polls the web site for the information it should pass to the displays. The cool thing is its all open-source. You can build your own Roominator for your company. All the source code and schematics are on Github.