Hello cuthechase we have a sample softphone to test the basic sip functions which we can give you. It is a windows based app which has all the underlying protocols of the SIP. In addition to being a head of development for this soft company I am also a Network Analysis Engineering and my work comprises of monitoring and correcting the UMG which has underlying protocols such as MGCP, H.248, SIGTRAN, SIP etc. In short yes we can develop solely for you. Hit us up if your still interested as dealing with communication protocols is my work which I do daily except on weekends of course.