Our Site

Completely functional app available at the Pebble Appstore! (Search "Jab")

Our Elevator Pitch

Until now, measuring improvement and tracking performance for punch-based athletics were difficult tasks, measured only by the face of your opponents. Now with Jab, an app for the Pebble smartwatch, you can analyze in real time the quality and quantity of your punching game. Through machine learning, Jab identifies when you are making a punch and calculates out a Punch Quality (PQ) value for you.


Rocky II is one of our favorite movies. We wondered what we could do for Mr. Balboa in the 21st century.

How it works

Jab uses the accelerometer in Pebble to detect jabs, compute the quantity and quality of jabs, and give the user feedback. In the app, there are two modes:

  • Strength Mode - Hulk Smash. You can too. Strength Mode will record the Punch Quality, a metric that combines power, rotation and technique. Jab will show you the best punch you've done this workout in addition to your previous and average Punch Quality, so you know just how hard you can hit.
  • Speed Mode - Speed Mode is built for long sparring sessions, tracking the number of punches you make and the average rate at which you let your fists fly. Ever wanted to know if you're the fast and furious, or the slow and steady? Speed Mode will let you know on the fly during your fight.


Up and down buttons - Toggle between strength/speed modes.
Center button - Resets the data.


The app initially tried to calculate punch displacement. However this took a double integral, which has insane error propogation and the lack of a gyroscope further complicated the calculation. Even with a Kalman filter the output was too far off. This challenge led us into making a more specialized application based on what we learned, leading towards the application that we have now.


We did some hard hard math, and the app is responsible, agile, and compact (Pebbles only get 25 kb of user RAM!).
And we have our first app in the Pebble Appstore, and a working product that we would be happy to use ourselves.

Lessons Learned

It ain’t about how hard you hit, it’s about how hard you can get hit and keep moving forward. That's how coding is done.

Future Directions

Training sets for punch types, larger RAM / better accelerometer. Only Pebble Time will tell.

Share this project: