Drowsiness Guard
Ten seconds
with your eyes shut.
Stand your phone on the desk. The camera reads how far your eyelids are open, and once they have stayed shut for ten seconds, it wakes you. Blinking never sets it off.
Watching
Eyes are open
The camera feed never leaves your device
Your alarm is probably the wrong frequency
A high, piercing beep feels like it must be the most wake-you-up sound there is. As far as anyone has actually measured, it is not.
Most smoke alarms sound a pure tone around 3100 Hz. Tested on sleeping people, a 520 Hz square wave wakes them far more reliably — and not by a small margin.
Those two figures come from adults with hearing loss, but the direction holds for children and for adults who have been drinking. It is why the US fire-alarm standard NFPA 72 now specifies 520 Hz for sleeping areas.
So that is what this uses. A square wave rather than a sine wave, because the harmonics stacked above the fundamental do part of the work. The rhythm is the fire-alarm T-3 pattern — half a second on, half a second off, three times, then a second and a half of silence — since the pauses turn out to help as well. A faint melody sits on top at 30% volume: flat beeping has been reported to deepen the grogginess you wake into, while melodic sound eases it.
Bruck & Thomas, Awakening of Sleeping People: A Decade of Research (Fire Technology) and the related body of work; McFarlane et al., Alarm tones, music and their elements (PLOS ONE, 2020). All of it studied fire alarms and waking from sleep — not desk-side drowsiness specifically.
Just put it on the desk
Stand the phone up so your face is in frame. That is the whole setup.
Not for use while driving. If you feel sleepy at the wheel, pull over and rest rather than relying on a tool.
Three ways to wake you
Use them together, or just one.
Synthesised in the browser, different per mode. Earphones are detected and the volume drops automatically — full blast next to your eardrum hurts before it wakes you. It plays down the media path rather than the ringer path, so it still sounds with the phone on silent.
Long, strong pulses, for rooms where you cannot make noise. Safari on iPhone does not support this — the page says so and switches it off.
A full-screen alert. Even with your eyes shut, the change in brightness can reach you through your eyelids. This is the one that works everywhere.
Three modes
The look, the sound and the wake-up all change together.
Bright and ordinary. Doesn't look odd in an office. Flashes red.
Every number it measures, on screen. Yellow-and-black hazard alert.
For a dark room. Never harsh — it brightens gradually.
The camera feed never leaves your device
Probably the first thing you want to know about a tool like this. No video and no audio leaves the browser.
- Nothing is sent to a server. All processing happens on your device
- Nothing is recorded. Only numbers are held, in memory
- You can hide the camera view and detection carries on regardless
- No account, no login
- Close the tab and nothing remains
For audio, only the rise and fall of the volume is examined. No speech and no words are analysed.
What it cannot do
- It stays silent when it cannot find a face. There is no way to tell whether you have stepped away or fallen asleep
- Glare on glasses, backlight, or a room that is too dark will degrade the eyelid reading. Your face needs some light on it
- Staring blankly with your eyes open is invisible to it
- “Head dropped”, “stopped moving” and “sleeping breath” are still experimental and off by default — they misfire
- Not a medical device. If you suspect a sleep disorder, please see a doctor
Add it to your home screen
It opens full-screen like an app, and starts instantly from then on. Nothing goes through a store, and it takes almost no space.
- Tap the Share button
a square with an arrow leaving it, at the bottom of the screen (at the top, on iPad) - Scroll down and choose “Add to Home Screen”
- Tap “Add”, top right
Other browsers, Chrome included, cannot do this. Reopen the page in Safari.
- Tap ⋮ at the top right
- Choose “Install app”
some phones say “Add to Home screen” - Tap “Install”
A prompt may appear at the bottom of the screen instead. Tapping that does the same thing.
- Click the install icon at the right-hand end of the address bar
a small screen with a downward arrow in it - Click “Install”
If you do not see it, look inside the ⋮ menu at the top right.
You will still be asked for camera permission once, the first time. Without it there are no eyelids to read.