The device in the original link is supposed to be viewed in the rider's peripheral vision rather than looking over to one side to squint at what data is showing.
The speed is shown as colour as well as number, for different roads, so it would tell you whether you're doing a speed under/over the limit of the road you're on. WITHOUT having to take your eyes off the road ahead. I think this would be quite a useful tool.
A lot of sports bike riders I know, use a DataTool's Digital Gear Indicator, which is mounted usually next to the clocks, so there are obviously many riders out there who don't automatically know what gear they're in, but DO want to know.