This article describes an extremely high-tech way of doing something that cars already do: tell you how fast you're going. Of course, throw in the term "Bluetooth," sit back, and watch the money roll in.
My grandfather's car had a device like this, and no, it's name wasn't "Grandma," although she was no slouch as a car kibitzer. She was the force behind its installation, though. Whenever Grandpa hit 55.00001 MPH, an obnoxious buzzing noise sounded (again, not from Grandma, although she contributed her share).