That's one way to do it except for us that can't get GV because google knows we're not in the u.s.
I avoid the call backs and just make it simple, call LD via sipdroid and pay the $0.01/min. Texting is very low on my list so I don't worry about it.
One handy thing is that I give out my VoIP numbers instead of the cell number. When called it will also ring my cell number so that I don't need to run sipdroid full time. I have local numbers and numbers in the u.s. and this ring group feature works great. If I travel I'll load Sipdroid and avoid roaming charges inbound or out. This way I can easily dump the cell service without the pain of loosing my cell number, I keep the VoIP numbers and don't care about the cell number.