【實用運動app】Freqmess|最夯免費app-gigacircle

With Freqmess you can measure the tension of the strings on your tennis racket. It makes use of the microphone to record the sound of the swinging string bed to calculate the tension. Just choose your setup, pluck the strings of your racket and hit the Record button.

More info at http://freqmess.roettig.org