Beating 81 with GT81

BEAT81 setup for outdoor workouts, with the screen showing the HR zone and % for each participant (source: BEAT81)

What is it

GIF of one of the earliest version of the app (with simulated HR)

How I built this

The app is in TypeScript, running on the wonderful React-based Next.js framework from Vercel, however, it could have probably been written in vanilla JS as well. It’s pretty much 100% client-side, with no DB or API dependency and all storage handled through localStorage. The whole (compiled) app would even fit on a floppy disk.

How can you use it

There’s a version running on my website — just go to, connect your HR monitor, and get started.



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store