Glad to see that lots of people like this. I can’t code so it’ll be really great if my suggestion can lead to something useful 
My own horror story that inspired this was looking for a hydrogen canister that I vaguely remember seeing in a lab. I only learned later that it’s a material for diamond weapons, so I searched through 3 levels of lab for it. I eventually found it but it was quite tedious.
As for the balance issue, I saw a relevant post about the game’s design against micromanagement, in this thread about field of view. It is a quote of a quote though, so I wish if someone can confirm whether it was the original intention:
Just replace “turn around” with “press V” and the quote fits perfectly. If the game already simulates the player character checking the surroundings, it really isn’t a far stretch to assume the player character is also looking for wanted items.
If it really is balance- or immersion- breaking to have your character noticing every little item around them all of the time (which now I’ve typed it, I can see how it really is bad for immersion), I’m sure something can be implemented to limit that. After all, I’m pretty sure (could be wrong) the V menu already doesn’t show all items on screen, depending on distance. At least it takes care of some items being not visible at distance, such as items in containers being only visible when the player is in an adjacent tile. I hope it wouldn’t be too hard to apply the same limit to the item safe mode.
Maybe the feature could only run when you’re idle or not in combat, for example when you press 5 to wait (but requiring a key input kind of defeats the purpose)? And distance, perception, lighting, item size, the amount of items on the same tile, and even speed at which you’re moving could all contribute to the spot check. I guess it all depends on whether the feature is really that balance/immersion breaking to require so much coding. And as the OP of course I’m biased towards implement first and nerf later as needed 
Lastly on the interface, perhaps at the very basic level it could be integrated into the autopickup menu? Have a shared list of items between the two features, while players can decide whether they want an item to be notified, autopickup-ed, or both. The more advanced interface feature I can think of is to add tools and materials through the craft, construction, and even vehicle installation menus.