A non-mechanical keyboard. I moved off of cherry style switches, and went with a topre clone. For me, the cherry mechanism makes too much noise when keys return back up. For me it was high pitched noise. A much more thocky keyboard actually keeps me from having noise induced headaches on heavy typing days.
Blue light reduction apps on phones, tablets, and monitor and blue light reduction coating on glasses. This removed a ton of eyestrain. Yes, my phone and iPad now have a reddish brown hue to them, but most of the time, I don't care. I hardly notice it anymore unless I use my partners device.
A color accurate monitor (with a good reader/blue light reduction mode). Having a monitor that wasn't close to having correct colors, even across the panel was maddening. Old LCD monitors are the worst. I don't need color correctness all the time, so the monitor needs a good mode to turn down the blueness. Having a setting in the monitor makes it a breeze to switch back and forth as needed.