Probably you’ve seen these punch games where you can hit a punchbag and see how hard you hit. Well you can build such thing by your own and enjoy your progress without inserting coins. All you need is an Arduino, accelerometer and some display to see hit expressed in numbers.
The biggest problem is to get a highest accuracy signal from accelerometer (ADXL193). Author decided not to use internal Arduino ADC, but instead he added an AD7580 16bit A/D converter so he could get more resolution and higher sampling rate. As a result it gives lots of pleasure to see you’re punching more interactive. Be sure to make soldering as tight as possible – as circuit deals with strong hits.