The GTalk2VoIP blog has details on how to call a GTalk user from a landline (or any PSTN phone including mobiles). It uses a gateway number provided by Sipbroker.com - with local number available in a wide range of countries. The instructions for use sound kind of complicated, but I suspect they in practice it isn’t as complex as it sounds:

  1. Obtain your own SIPBroker ID from your personal page on GTalk2VoIP (follow the link displayed by MYPAGE command).
  2. Choose one of the available PSTN gateway numbers. Complete list is at http://www.sipbroker.com/sipbroker/action/pstnNumbers
  3. Dial the PSTN gateway number from your mobile or any other phone.
  4. Punch in your SIPBroker ID using tones (DTMF) at voice prompt and wait incoming call to your Google Talk.

I haven’t tried this yet, but I’d be interested to hear from any readers who get it working with GTalk, or any other SIP based software. For instance, in theory this should work fine with Gizmo.

Updated: It is very easy to do this with Gizmo - go to the SipBroker.com list of access numbers, dial one, then enter your Gizmo SIP number (found by going File->My Profile and looking in the “SIP number” field). That’s it! I’ve yet to have the same success with GTalk, though.