OctroTalk version 1.0.5 now lets you make audio call with GoogleTalk/Gmail buddies.
You can upload vCard images by tapping your vCard photo on the buddy list. Have added Sounds and Vibration preferences so that you can
enable/disable sounds/vibrations.
In the voice call feature, even though we did our best, there are still some known issues -
1) You cannot play the sound through the headset. There is no API to route audio through there. Ask Microsoft for help .
2) There is about a 1-2 second delay in playing remote voice. Again, a problem due to the APIs.
3) Echo - since we can't use the headset, and there is no echo cancellation API.
4) Incoming calls don't ring if your application is in the background.

The new version can be downloaded from the Windows Phone Marketplace at -