My experience with all bar the really old all rubber Garmin HR straps was they were influenced a lot by wind, and clothing. The Fabric Chest Garmin less so. I tried a Mio wrist one and its fine except when exercising on a bike.
Not tried the arm ones but maybe the same for that, I think the main problem is the lack of sweat in the wrist as well, so this might make the arm one have the same issues I had. If you do have any issues I did read that Bah-Bump (Electrode Cream) helps in areas that do not stay moist enough. When I was really in to it, I came across a base layer one but it was enormous £££'s