Of course that limits you to the "Groove enabled car". And that only refers to actual SMS messages which go through the cell phone company. It wouldn't affect "Skype" type text messages, iMessage, or any other messaging service that uses internet data plans, instead of SMS messages. That "data port" (I assume they are talking about the maintenance error code reading port) may already be used by numerous other devices on the market already.
Another way to deploy this kind of thing, without requiring any external device, or cooperation with a cell phone company, would be for software in the Smart phone's operating system that automatically disables text features, and optional "apps" like Skype, when the cell phone's internal GPS senses movement.