Appear.in is great, but like all the other WebRTC chat services, you still need to use another method of communication to notify the other part(y/ies) of the call either by phone, SMS, IM, email, IRC etc. so they can then click the link to your chat and grant their browser permission to use their mic and/or camera, IF their browser is up-to-date enough, and not Safari. ... That's what makes these otherwise perfect services suboptimal for the majority of non-techies.

Which by the way works very well for our daily meetings.