How to activate the Google Voice app?

[AllThingsPure]

I have a Google Voice number, but now I am outside the US using a foreign SIM. This is when I need GV most. But when I start the GV app on my Galaxy Note ICS, it apparently tries to send an SMS from my foreign SIM to Google. This was not successful.

Why is a SIM necessary to activate GV when the whole idea of GV is to avoid using normal carrier telephony?

Is there a proper way to activate the GV app to use my GV number when outside the US? Thanks.

PS: I have no problem using GV on my PC using the Chat app whenever I signed in to Gmail, even on foreign networks.

 

[Crashdamage]

GV will not work outside the US using a foreign SIM.

 

[AllThingsPure]

Thanks. The requirement is a bit odd.

Does it also mean that if your GV app on the Android phone is working, in the US, and you change your SIM, you have to re-activate or re-register again?