Chris of PyroElectro Microcontrollers has a DIY guide post on how to make your own Personal G-Force Meter:

The main application of the accelerometer is either for sensing tilt or sensing acceleration. For this application A G-Force meter for my car will be made to see how many "G's" I pull while driving.

I drive like a grampa, so I'm sure my Personal G-Force meter will flatline near zero: Link - thanks Chris!