How to call GTalk to GTalk from Android? I need it badly. I know Google voice is there, but it's not available in India.

Clarifications
Need any good client application (Google Talk / Jabber client) that supports voice calls to and from GTalk users.

Thanks @Matthew
Google Talk Video/Voice support will be rolled out shortly on all Android 2.3 Gingerbread devices or on the Nexus S now (but as an OS update, not an app update, so you would find it in Settings, not in Market)