We need a SIP softphone built using Flash, so that the phone can be embedded in a web page and be used to make calls directly from that page. We'll also need the corresponding server side work done to bridge between the phone and SIP, and Flash's streaming audio format and G.711.
Configurationwise, the Flash part will be passed a parameter when it is downloaded, which identifies the phone, and this parameter will be passed back to the server when a call is made. The server will use this parameter to look up the SIP server and account details.
The deliverable is the phone and the server side, installed on a VPS which we'll give you access to.
Google for Red5Phone for something which does most of what's needed.