I thought I'd make a bundle coming up with the idea of giving cruise-control systems awareness of hills and allowing them to back off near the crest of a hill and accelerate a bit before the base a hill, but it's already been patented
. The idea has been introduced
, but I'm not aware of it ever catching on.
I suspect a major drawback to a company interested in promoting this system is that by design, it would introduce speed variances
between equipped cars and non-equipped cars, which opens the door for accidents and litigation.