The Tether Mac OS app + Tether iPad app work in tandem, so you'll need both to get started. The Tether iPad app is available for download on the iTunes App Store: http://itunes.apple.com/us/app/tether-interactive-whiteboard/id473781122?mt=8
MOBILE COMMAND STATION
Tether connects your computer screen to your iPad, allowing you to control the presentation easily, intuitively and from anywhere in the room. When tethered, your stationary computer responds in real time, so what you do on your iPad instantly shows up on the main display.
Tether makes it easy to remotely control your computer by turning your iPad's screen into a mobile track pad. There's no monthly service charge, and you don't need extra equipment