Not sure what you mean by hook, the hook switch in the 'phone maybe.
I think what needs to be done is to have s client running sip protocol on the network, and define a ringing group on the server, so then the server sends the invite command to both my phone and to an arduino running sip protcol, said arduino can then control a relay for the ringer, turning it on for a invite and off for a bye command.
I'm fairly well versed wth C++, never seen tuniot before.