Recording

I was wondering if there is a way to create a virtual extension that I can only use for recording. The reason for this is I wanted to use freepbx as a recorder when a client has an existing PBX but only needs recording. My plan was to split each extension into two parallel channels from the PBX and connect one end point to a freepbx server with fxo ports and the other endpoint to the phone itself so when a call is made or a call comes in that the telephone still receives signal from the PBX and I can capture that signal on the freepbx server as a recording. Any help or ideas would be greatly appreciated.