Your laptop was already listening.
Bonk just answers.
Every Apple Silicon MacBook ships with an accelerometer. Bonk reads it and turns physical knocks on the chassis into actions — no extra hardware, no cloud, no subscription.
What it is
Bonk is a tiny macOS menu bar app. Knock once, twice, or three times anywhere on your MacBook — palm rest, lid, next to the trackpad — and each pattern runs whatever you've bound to it: media controls, lock screen, a keyboard shortcut, an app, a shell command, or a Shortcuts.app shortcut. You can even give each of your apps its own mappings, so a double knock means one thing in your editor and another in your music player.
How it works
- The accelerometer is read ~100 times a second through IOKit — the same sensor that helps your Mac detect sudden movement.
- A slow-adapting baseline tracks gravity, so tilting or carrying the laptop doesn't trigger anything. Only sharp spikes stand out.
- A spike counts as a knock only if it's brief (sustained vibration like fans or desk wobble is rejected) and you're not typing.
- Knocks that land within half a second of each other group into a pattern — single, double, triple — and the pattern fires your action.
You can watch all of this happen on a live waveform in the settings window, and calibrate the sensitivity by simply knocking three times.
Why it's free
Apps that do a fraction of this charge for it. Bonk is free and open source because a feature this fun shouldn't sit behind a paywall — and because the entire app runs on your machine, there's nothing to host and nothing to charge for. If you like it, star it on GitHub or contribute an idea.
Fully local, by design
Bonk makes zero network calls. No accounts, no telemetry, no update pings. The knock data never leaves the sensor loop, let alone your machine. The privacy page spells it out.