I faced the necessity to introduce a sip phone to the browser. On the internet mostly is the information on the basis of red5 + red5phone, but it seemed a bit of crocky and insufficiently reliable. Let us just say I was not satisfied with the time correlation of deployment and the required hardware resources to a level of quality, support, and ranging, also it is problematic for integration in a web project.
A little more searching I found this one project on the internet. It makes essentially the same as red5, but it is written in python and it has a flexible web interface.