"MFI - Magnetic Force Indicator" is an app that specializes in displaying the magnetic field data acquired by the Apple Watch as numerical values, by removing functions such as notification, sensitivity adjustment, and noise reduction, which are included in "SMD - Simple Magnetic Detector." It provides easier visualization by performing stronger noise reduction and slowing down the fluctuations in the numerical values compared to SMD.

It can be used to easily observe changes in magnetic fields or to check whether an object is magnetic.

- Due to the specifications of the Apple Watch, the display stops when the screen goes to sleep. Therefore, it is recommended to set "Wake for 70 seconds" in "Settings > Display & Brightness > Wake Screen" when using the app. Also, keep in mind that the screen goes to sleep even if you lower your arm or tilt the watch outward, so always keep the screen facing towards you.
- Please be aware that if a strong magnet is brought too close to the Apple Watch, the detection may stop and the display will show "0.0" for a while. However, the app can be used again after waiting for a few seconds to a few minutes.
- his app cannot be used on Apple Watch models earlier than Series 4 that do not have a built-in magnetic sensor.

While not its intended use, the app may also be useful for detecting hidden cameras, as they may contain electronic components or magnets that generate magnetic fields. However, please note the following issues with using magnetic fields to detect hidden cameras:
1. False positives: Other electronic devices or metal objects can also generate magnetic fields, which may cause false positives.
2. False negatives: Some hidden cameras may not generate any magnetic fields or generate very weak magnetic fields that cannot be detected by this method alone, which may result in false negatives