...numerous high-end vehicles have clinometers (or, inclinometers) built into the electronics (as an electronic sub-system; ie. you are not able to tap into it). These devices are used to auto-adjust suspension on the fly, engage descent control automatically, any myriad of other functions). Also, some GPS units have a clinometer built into their electronics, easily accessible by the user (check your GPS for this function).
If you want one of these devices, they are available as stand-alone dashboard peel-and-stick consoles for very cheap: $19 to ~~$45 US dollars (orderable on-line from numerous Internet suppliers).
BTW: your smartphone has dozens of scientific instruments already built into it (accelerometers; clinometers; heat sensors; proximity sensors; and many, many more instruments (get the appropriate free Android/Apple phone application to drive your various smartphone sensors).
thanks, but I'm the only person on the world without an smartphone.
my garmin dakota 20 has an inclinometer, but that gps I dont use in car. There is an pc5600 with an mirror monitor. But without an inclinometer. So an external one is what i want.
On ebay I see a lot of them, but the quality........
so that why i was wondering if others have one in there car and if they like it.