SIP Client in Rails App

Hey,

do you think it could be possible to integrate a SIP or IAX client into
a Rails app to use it for VoIP calls directly from the web page by
clicking a link without having to download a 3rd party client?

Is there any other solution than an activeX control to access the
microphone?
Do you have made experience with a free minimalistic applet or activeX
control?

Greets

I have no experience with this at all but I know Flash can access the
microphone. Maybe a Flash/Flex solution would work.

--Jeremy