Rearview mirror at the top of my 52" curved widescreen monitor. I work at home in limited space with family around and there's always activity behind me, doors opening, etc. I also work with noise cancelling headphones. Hard to explain why, but the mirror stops my constant need to turn around to figure out what's happening. It took me a minute to hang, with fishing line and zip-ties. Way less cognitive overhead and fewer self-made interruptions since implementing this. $13 - https://www.amazon.com/dp/B08MFD7BT7