SRTP support
problem
Gajim doesn't support Secure RTP for jingle calls.
analysis
The SRTP support is required by WebRTC specification so the Gajim need to support it in order to be able to make calls to VoIP web applications.
Protocol description: http://xmpp.org/extensions/xep-0167.html#srtp
enhancement recommendation
Unfortunately, I don't know any existent Jingle implementations that supports SRTP to test it (except of probably jitsi but I can't test it anyway and it prefers ZRTP but probably can serve incoming SRTP calls as well).