asterisk users - Dec 2007 - get REMOTE SIP extension status without calling it

Hi

This is not the same thread. Right now I?m asking about REMOTE status.

I need from my asterisk to keep track of a remote (another sip server) 
extension status. It?s not needed to know if it?s busy or DND, I think 
for me would be enough to know that the user is connected at the remote 
sip server.

I think maybe sending and OPTION messages it could work but i don?t know 
how to send it f rom asterisk dialplan.

Thanks