What is Reddit's opinion of Gauss Meter?

From 3.5 billion Reddit comments

You can easily check if it's perhaps slightly magnetized.

Just use a small compass and see if the needle deflects around the watch, or use an app on a smart phone with a magnetometer (practically all have this sensor...). Something like Gauss Meter on Android, for example.

Alright, one playStore app actually displays mG (milliGauss) instead of uT (microTeslas)
https://play.google.com/store/apps/details?id=com.keuwl.gaussmeter&hl=fr&gl=US
And it displays between 0.1mG and 0.3mG in my room (medium size living room in a big tower)
So 20uT probably translates to 0.2mG (google search says it's 50 times more though, but probably the culprit are the app displaying uT. so just find a mG app to check if you are under 0.4mG.)

In this case I'd also suspect that it's magnetized.

You can do a preliminary check yourself, if you have a smartphone with a magnetometer. Most modern ones should have this sensor...

On an Android, you can use an app such as Gauss Meter. Just hover the phone around the watch and see if the readings start to deviate a lot.

A small old fashioned compass would do too.

If not, a trip to a watchmaker and a timegrapher will be needed...

There is usually a sensor in the phone that can measure magnetic fields. It is used for providing compass direction in some apps. You can get apps that show the data that this sensor senses.

I've played around with them over the years. The only things you'll be able to detect are magnetic fields and/or whether a ferro-magnetic piece of metal is near the sensor.

You won't be able to detect electrical current or radio waves.

Search for EMF detector, metal detector, or magnetic field detector. Find the one with the fewest amount of permissions.

This dev has some cool apps:

https://play.google.com/store/apps/details?id=com.keuwl.gaussmeter

Shouldn't be a problem. And if you like, for a bit of peace of mind to be 100% sure you can try sticking your phone on top of your PSU with this (or this if you have an iPhone) on and seeing if there's any difference

https://play.google.com/store/apps/details?id=com.keuwl.gaussmeter&hl=en

No idea how accurate it is but it seems pretty cool.