I like the "alert me when available" feature of sametime. However, if someone is on the phone they are not available. So I would like to be alerted when they are off the phone or VC.
I think Sametime Unified Telephony would allow this (if you dial from a phone associated to your unified number). If you only look for Phone presence (on or off) into Sametime (without click to dial, unified number and other features offered by SUT) you could use the phone presence synchronisation solution offered by a german company called iLink, it is a subet of a product called "ioffice communicator for Sametime"