Apple TV hacker l0rdr0ck put together a procedure for getting Asterisk running, turning the Apple TV into a telephony appliance!
To get Asterisk running on Apple TV requires (obviously) and Apple TV. It also requires an Intel Mac, as there are no development tools available on the Apple TV (yet). We’ve divided the process into three steps: preparing your Apple TV, building Asterisk on your Mac, and finally installing the compiled Asterisk code onto the Apple TV.
Install Asterisk on Apple TV –Link.