Voip web client

I have been Googling all day for a web client which features voip. So a button on my website which my visitor can click so he can talk to me.

With the jingle support I thought it would be already a feature in Openfiire but the Spark client that supports talk is a standalone and not a web client (the web version does not have this functionality).

Also Google Talk, the web-version, does not have Talk.

Other commercial companies make you load an ActiveX-component.

so my question. Is it possible to use or extend Smack, or the Openfire system, to develop such a functionality, or does it have particular difficulties to do this (why would not Google Talk support it, is that a bandwidth problem?).

Any suggestion is welcome. I would really like to have this feature on my website, and if the development is straightforward than I will find the resources to do it.