The schematic show that the AccelR8 only uses 3 IC's. An AVR 8515 microcontroller do the calculation work and controls the other circuits. An MAX603 controls voltage and power-on/power-off. And the chip that makes it all possible, the ADXL202 from Analog Devices measures the acceleration.
This chip is a small wonder. It uses a tiny micro machined polysilicon structure on the silicon wafer. The structure is part of a capacitor, so deflection of the structure (by acceleration) can be measured.
The ADXL202 can measure acceleration in two axes, and if you have a Microsoft Freestyle Gamepad, you already have an ADXL202 !
In this case, we only use one of the axes, and the ADXL202 outputs this data as a variable duty-cycle squarewave. The 8515 calculates the acceleration by measuring the pulsewidth/period relationship. The acceleration is then used in further calculations, and the resulting data is show on the display.