The prospect of simply coding a SIP “Click To Call” type interface into your web site or App and having it just work on any advice is definitely still a dream presently. But if WebRTC and SipML5 continue to progress down their current paths, we may not be too far off.
According to SipML5
The technology however is still in its infancy and deploying it in the wild would require users to be using some bleeding edge browsers. There is some differences in the data from the projects, with SipML5 stating that you need to be running firefox nightlies, while WebRTC says the stable versions are ready. Also if you want to use it with say, Asterisk, get ready to set up a testing VM to recompile.
Go Ahead and experiment, develop a cool click to call code snippet or widget for WordPress and I’d love to use it. For now I’m still looking for a good FOSS solution for this application.