Yes, the original soundracer plugged in to the cigarette lighter and ran through the internal speakers.
The new system they have will run through an external speaker, and the speed info can be fed to their system by the OBD port.
In the US, rather than have legal issues with trying to replace the factory AVAS people are looking at ways to make noise in addition to it - if it's louder then there shouldn't be an issue.
It can always be switched off and the factory fitted AVAS will still be there.