[Perfectlap]

I too have wondered why the others haven't come up with something similar. Not necesarily an arrow but perhaps a unique audible alert that would indicate you've gone past it. You know so you can exhale and quit looking in that rearview.
The patent must cover that part of the warning system because I'm sure I'm not the first to come up with this idea.
As for the patent expiring I'm sure like the pharmaceutical mafias they'll just slightly tweak it to get a whole new patent issued.