I made for a bit of dashboard flair with a G-meter (g's-meter?). I made this with my "Idea Box", this particular one features an SX28 microcontroller, and its 7805SR switching regulator makes running from 9V batteries very practical. I suppose this project could be accomplished with most any microcontroller. The SX28 has been EOL'd, but it's a wonderful little "chip" and I have a lot of them.
If you're into "gee jobs", pun intended, then this is for you.
The acceleration/deceleration is sensed by one axis of the Parallax 2-axis accelerometer (available at RadioShack). The accelerometer's variable pulse-width output is read by the SX28. The microcontroller updates the LED display. The display LEDs, 5 Red-Green (3-lead) LEDs, light Green from left to right with increasing acceleration and Red from right to lift with increasing deceleration.
Just read the accelerometer's output pulse width and then determine the bargraph result of that reading and repeat (an infinite loop.) The time between readings came help to dampen any jumpiness. So, the two parameters are: your ranges (a pulse between [n1] and [n2] results [x] LEDs, and so on) and the time between readings (read PW, hold/pause, read PW, hold/pause,...).
Some photos and a schematic follow.
Here's a link to an online vid, seeing's believing.
-- PJA --