Agreed -- But how is the child better served if 911 connects them to a call center which might not even be in the same state, and all they know is that they're at dad's house?
Having 911 (or better, E911) for a fixed location VoIP device is already being implemented by many/most carriers that sell a non-portable solution.
However, making roaming 911 work is a challenge which won't be overcome easily unless you can force users to enter a current valid address whenever they move the VoIP device. It's virtually impossible to get reliable GPS signals indoors, so it simply isn't feasible for the device to do the trick itself. Cell phones at least have a fixed location of the tower, which can give the call center a rough idea of where the problem is, but VoIP doesn't even have that advantage.
I don't know about anybody else, but I'd rather have 911 return a "Stop, this phone is not equipped to dial 911. Please use another phone to dial 911" error message rather then have someone get routed to a 911 call center that can't help them -- At least knowing that no help is coming gives them a chance to obtain assistance elsewhere.
[TELECOM Digest Editor's Note: I wonder how this scheme would work ... any calls to 911 from a VOIP get intercepted by the broadband ISP who is handling the connection. The IP address in use (and its physical address) get transmitted 'like ANI' to the local police. The 'ANI-like' information passed along (from wherever) to the PSAP identifies it as a VOIP from address (registered with the ISP for the IP street address.) Am I correct in my assumption that most stationary computers with broadband stay in the same place and they are almost always on the same IP address as well? I know in my instance I have been 24.xxx.xxx.xxx for however long, here at the same street address, etc. Can't those two items (IP and street address) often as not be matched? PAT]