While doing some weird keywords combination on Mountain View's search engine, I ran across this interesting application allegedly called "Vomit", which means "voice over misconfigured internet telephones":

The vomit utility converts a Cisco IP phone conversation into a wave file that can be played with ordinary sound players. Vomit requires a tcpdump output file. Vomit is not a VoIP sniffer also it could be but the naming is probably related to H.323.

The vomit utility is distributed under a BSD-license and completely free for any use including commercial.