I actually don't know if Google Voice has that capability unless you hack it by having each phone logged into the same account.
The biggest benefit for me with StatPhone is the incoming callerID is the StatPhone number. So even if the kid's school is calling from a random number, on your phone it shows the StatPhone number and you know its a call pertains to your child.
Also grouped escalation, so if my father calls in an emergency, the kids get called first and then the in laws and our uncle.
