[SR-Users] Is this idea even feasible?

Hi. I'm looking for a solution to the following problem, and wondering whether Kamailio (with which I have very little experience so far) may be it, or whether I'm thinking in totally the wrong direction. The problem: I have a SIP client application which runs on a standard Linux system, and is extremely basic - it can REGISTER in order to receive inbound calls, and it can send INVITEs in order to place outbound calls, and that's about it. It handles media as well - in essence, it's a simple softphone. I can't change it for a more capable one, before anyone suggests that :) Specifically, this thing cannot send REINVITEs in order to put calls on hold, nor can it handle anything to do with transfers (blind or attended). I'm looking for something which does have these SIP capabilities which I could put in between this application and the SIP server through which it is placing and receiving calls, so that I can (through some sort of API) cause calls in progress to be put on hold, resumed, blind transferred, or hold-and-attended- transferred. Does that sound like something Kamailio can do? If so, can anyone point me in a helpful direction re how to go about it? If not, can anyone suggest something else which could sit in between a very basic SIP client and a PBX server, in order to inject these sorts of commands into the path and thereby give me these sorts of extra call capabilities? Thanks, Antony. -- I'm not impossible, just highly implausible. Please reply to the list; please *don't* CC me.