1: You must use a mobile device with an accelerometer (tilt sensor) and magnetometer (compass).

2: We recommend using the Chrome web browser. However, you have to ENABLE SENSORS IN CHROME FLAGS. Cut and paste the following address: chrome://flags/#enable-generic-sensor-extra-classes then enable "Generic Sensor" as well as "Generic Sensor Extra Classes" flags

chrome flags

About Face Guardian: Face touching is one of the primary ways coronavirus is spread. This app lets you use your phone's compass and a magnet on your wrist to detect face touching. It is designed to increase awareness of face touching or outright prevent it. Face Guardian is a CMI MATTER Lab project .

Developer? This project welcomes contributors.

info   X  

Android Chrome only for now


1: Wear smartphone around the neck as close to the face (high up) as is comfortable.

2: Wear a strong magnet on the bottom of one or both wrists.

photo magnet on wrist

3: Use a mirror to view phone (press "MIRROR") or use a webcam to view phone.

4: Press "ADD OFF TARGET" while wrist(s) is *away* from face. Wait for 100 samples to collect.

photo collect off face

5: Touch (clean) hand to face in a naturalistic manner so that magnet approaches phone. Press "ADD ON TARGET" while your hand is touching the face. Move hand around to different positions on your face as 100 data samples are collected. You want to capture as many possible face touching gestures as possible.

photo collect on face

6: Once 100 samples of on and off-target data are collected an LSTM (Long Short-Term Memory) RNN (Recursive Neural Network) model will be trained to classify (detect) the face touching gestures captured in the "on target" training data.

photo detect face touches


*You can toggle vibration and audio alerts in the settings page.

*To test a magnet, place phone on a flat surface and press "TEST MAGNET" while no magnet is close to the phone. Approach the phone with a magnet. Observe the distance of the magnet from phone when the "TEST MAGNET" button turns from red to green. This is the maximum range of the magnet. If the distance from the magnet on your wrist to the phone around your neck exceeds this maximum range the app may fail to detect a face touch. The test displays the net change in EM field strength. The range threshold is about 10 microteslas (uT).

photo test magnet

*If you don't have any magnets you can still try out the app by using the accelerometer "phone on arm/hand" setting. Attach phone to arm or hold in hand and pretend to touch your face (or do so with clean hands). Gather ON target data while touching face. Move arm around in a variety of ways while gathering OFF target data (Egyptian epileptic snake dance is best).

*"Delta" data refers to classification between relative changes in EM field strength vs "Absolute" which refers to classification between discrete EM field strength measurements. "Absolute" will only work if you always face in the same direction as you did when you gathered training data. This is because of Earth's magnetic field. "Absolute" data setting is not very practical but it requires a less powerful magnet an provides a clean looking demo.

Sensor Selection Settings
Alert SettingsMax 2 Targets

Sensitivity: medium

Data Setting
Streaming Data

Not Connected