Do you concider sippy B2BUA?

hmmm, 5 minutes in thier web site and B2BUA looks kind of close to what I want ... Merci Alex.

OpenSer will not do what you require, go back to asterisk

I have worked on Asterisk & I have come to believe publicity have made him a Hero while he is not and maybe will never be, so if I ever go back to anything else it would be callweaver.