The closest you would come to a "bridge appearance" would be an autodial button for the extention you want to monitor. It would show you when the extention was in use vs. idle and you could dial it with one button touch. However, if you want the other extention to physically ring on your phone - you would need a "cover button" for it on your phone.
Tom Daugirdas,
President
STCG, Inc.
stcg.com