Asterisk 1.8, freeswitch, and freepbx (paid version) all support using XMPP (a google chat account) to make outgoing and incoming calls via google voice. Pidgin is able to receive incoming calls. Sipsorcery is also working on support, and has posted some details on how the protocol works here. Android is rumored to have the ability to make google voice calls via data in gingerbread (I have no clue if this is actually true though).

Native support for calling via google voice account using a google chat account directly in maemo would be awesome. I have no clue what is involved in this (can the current google chat plugin be modified, or would a new one have to be created?).

If enough people are interested, perhaps some type of bounty could be posted for this feature.

Thoughts?