[nabusman]

I used to use Skype for this when I was traveling outside the US. I also imagine you can set up something simple with Twilio as well, IIRC they have a no-code configuration tool for this kind of thing (simple forwarding, text to email, etc.)

[gst]

Main downside of Skype is that you afaik can't port a number into it. Otherwise it would be a great alternative to Google Voice.