Have you not noticed that I look at my speedo every 5 seconds or so? I do the same with my mirrors. But did we drive off the cliff? Or hit an oncomming car? Nope. I know I'm giving humanity a lot of credit with this... but I'm sure people can learn to glimpse at their speedo and learn how to maintain speed.
Really though, if people are that useless that they CAN'T monitor the instruments in their car for fear of hitting something/someone... they really should hand their licence back in.
I also like that this will stop alot of those +10% people. You know the ones. 55 in a 50 zone, 66 in a 60 zone, 121 in a 110 zone. Those people annoy the crap out of me.