What exactly are you wanting to monitor about the phone? I know for Cisco IP phones, you can browse to the IP and get some basic config info, download logs look at a bunch of network stats, etc..
Are you looking to monitor jitter? looking for a MOS score?
I doubt Solarwinds has the mibs for the phone, but - see if you can browse to the device - maybe you can see if it supports snmp.
i searched up the bim and should be able to import it.
as far as what to monitor...
i dont know.
this is just and experiment to see whats available and whats possible.