Please check out the punch acceleration sensor i've built to measure a strength of the punch as it lands on the target. ADXL193 250g single axis accelerometer is used to measure acceleration which is then sampled using AD7680 16bit A/D converter. Arduino computes maximum acceleration in G and displays it on a 7 segment LED display:http://abieneman.wordpress.com/2010/04/04/punch-acceleration-sensor/
Detailed description of results and hardware as well as drawings and Eagle files are available. Software description coming soon.