I did have a smart tag I told my daughter to take out with her so i could see how it worked. Well she lost it went to where last location was but couldn't find it.
so from my experience the tag would be best for keys for house or car keys etc not useful for outside.
they're very useful, if like me you always lose your keys around the house. I wouldn't pay full price for one but they are OK if you got it as a freebe with the s21 upgrade