The inclinometer has no way of knowing that you are on a short dip in the road, or a long hill.
Maybe the inclinometer output could be logically ANDed with hill data on file and a GPS to tell the controller where you are.?.
A few years ago (1998), I was thinking about some 'Electronic Counter Measures' using GPS w/ a CPU to memorize the RF spectrum vs location, I sent some ideas to the makers of Radar Fuzz-Busters, got no replies.
Now I see that one of the companies might have read their email.
Since they are now selling a Radar Detector with built-in GPS so they
can map out false-alarm areas and areas where known speed traps exist.
It works as an early warning system, (before you enter the trap area).
Uniden | A World Without Wires - GPSRD
A similar program could be used to map out your area for good coasting hills using a
learn mode. Otherwise, it would have to use a large pre-made data-base of hill data.