Getting the caller ID from a VOIP connection

[Damien P]

I was asked the other night about using Asterisk to show the incoming caller ID on a TV (I'm sorry but I forgot your name).  There were two VOIP connections available, and I considered sniffing the SIP connection, but since the VOIP ATA was built into the modem, this wasn't an option.  I thought that using Asterisk was like putting a nail in with a steamroller, but I came across Sipsak:

  http://www.sipsak.org/

It's a command line tool for diagnosing VOIP connection problems, but among the things it can do is to register with a server and show the headers, which seems like exactly what could be used here.  The "screenshots" show the headers, which include the incoming telephone number.