HandSpeed Turns a Boxing Bag Into a Timing Instrument

Field notes

HandSpeed describes an acoustic calibration process in which the iPhone learns the sound of a particular heavy bag before timing impacts and responses. The listed training modes include random-cue reaction rounds, punch counting, and 15/15, Tabata, and 30/30 intervals. The page reports metrics such as median reaction time, punches per minute, per-sprint counts, and drop-off, while its accuracy and 2-millisecond resolution figures remain site-stated claims.