For ergonomic typing you actually should never be resting your wrists while typing - so it's less that it "makes up" for not being able to rest my wrists, and more that it encourages good habits by not making it easy to rest my wrists while typing.
For when I'm not typing, if I wanted, I guess i could buy something like this for either side, but honestly i don't find myself needing it - I generally either keep my hands in the typing position while I'm working or have them in my lap when I'm reading.
I will admit though that I do rest my elbows on my chair's armrest while typing, which you're not actually supposed to do, but as I understand it, that's a relatively negligible point