CyanogenMod/android_packages_apps_VoicePlus — pull request #2 by zx2c4 (2013-09-23 23:52:34+00:00)
Title: Only send US numbers over GVoice

Google Voice only allows sending SMS to US numbers. On non-US phones,
it makes sense to send normal SMSes through the normal cellular channel,
while sending US SMSes via GVoice. This is, at least, the most common
work flow for non-US phones that use GVoice.

This patch is untested.