ArBPM

ArBPM is a Beats per Minute counter. This means it can measure the rate of anything you want, from music beats to heartbeats and writing speed. It´s a very small window that you can set on top of other windows and, by hitting any key on the keyboard, it measure the rate, showing the results in BPM, Hertz (Beats per Seconds), Beats per Hour or mean time interval (in Seconds). Skinnable and Freeware.