Dust plug

In my opinion if it was needed then a Garmin would have fitted one like they do on Edges.

Not for that price... And maybe with a plug on your FR935 (or any other compatible watch) you could have the same issues as with the first Polar M400 design, which also had a plug for the charging port (which is USB on the Polar M400). Said port corroded in certain units because of humidity that couldn't escape. So if you want to buy it, always make sure the port and the plug are dry so as to avoid any (possible) corrosion.

Interesting, first have heard of this. Guess it is a bit like screen protectors. Some people swear by them, I never bother and Garmin never bundle one with a new watch.

If you are asking do you need one then no is my answer.

Seems pretty useless to me...

The charging connection is not open anyway, at most some dust might gather in it but just blowing in it or something would clean things up... It's not as if it can get into the watch. Also, you have it on your wrist a ton of time probably, so dust won't get in anyway.

I just clean it a bit after running (and dry it after a shower) which seems like more then enough to me. And indeed, especially for that price...

I would lose it in the first week for sure.

No, but I do admire the unrelenting nature of capitalism.

Also on Ebay for 1,89$: http://www.ebay.com/itm/10PCS-Wristb...EAAOSwPyBZtkKd
I'm giving it a try.. anything that might alleviate my skin irritation is welcome.. but I'll probably turn out to be hopelessly allergic to the material that the plugs are made of.

I would have thought would make skin irritation worse as you would now have almost certainly have some plastic touching your wrist that you would not have done previously. And its going to get caked in invisible sweat....

I've been using one of the 10 plugs that were in the package for a few days now. If you use the OHR I can't recommend it, because the plug sticks out a little bit and the OHR sensor leaks more light when the dust plug is in place.
If you're considering to use these to alleviate skin irritation, a piece of tape on the back of the watch works just as well. The only advantage of the plugs is that no adhesive residue is left behind after removal.
If it is worth the 1,89.. only if you're tired of using tape, I guess.