Code for detecting G-forces for braking and accelerating when driving a car

Hellou! A tiny Android app needed, that gives me braking and acceleration g-forces when driving a car. For example, if I drive to direction 127 (360 degrees system) and press the brake pedal, it should give me braking g-forces for driving direction 127 (plus minus few degrees tolerance is ok). If I shake my phone from degrees 37 to 217 when driving , it should not affect the braking (and acceleration) G-force values. Please check out Android App "Smart Speedometer" from Google Play, Braking and Accel tabs. I need just the g-force values on screen (and the source code of course), no graphical bars needed. The goal is to compare driver's driving behavior compared to other drivers. I tried to code this by my self with one year experience of Android coding, but got stuck with the accelerometer values when driving a bumpy road. Target platform is about 70% of latest Android devices currently on market, no need to cover all devices. "Keep it simple" is ok. Keywords: GPS, Android, Location, Accelerometer, G-forces