Based on the ADXL322 solid-state accelerometer and the ATTINY26, I built an instrument to show the lateral and longitudinal acceleration.
Circuitry with ADXL322 accelerometer Atmel ATTINY 26
The left column of the instrument shows the instantaneous values, the right column the highest value measured during the past 5 seconds (so you can keep your eyes on the road in a turn and still know the g-forces ;-)
The picture below shows the current installation of the display above the radio.
The prototype looked like this: