I know that WebRTC
was designed for browsers, but is it possible to use WebRTC libraries on mobile applications directly?
Thanks!
You could use WebRTC with native apps, but it requires a bit of work.
If you look at the image you can see a red rectangle at the bottom. That's the native C++ libraries of WebRTC. The WebRTC classes and WebRTC objects for audio and Video can also be found as part of the WebRTC project.What you would need to add is an API for your app to be able to setup calls(The VOIP interface), a signaling stack and NAT traversal utilities(Core Protocol- For SIP this could be something like PJSIP and PJNATH) and an adapter from your signaling stack to webrtc, telling it when to open channels for video and audio and when to stop them etc.
See also: http://bloggeek.me/porting-webrtc-mobile/