[mikeejimbo]

I dunno, even in a Modular Abilities slot this proposal is more limited than being able to detect anything. Since it's a specific object, the caster has to know it exists. Arguing that he has to be familiar with it - actually seen it in person at least - is probably reasonable. Even extending that to things he hasn't seen in person but knows exists probably isn't too bad. Maybe the caster can attune to the Codex Hammer even if he's never had it. But if he's searching for a rare book, but doesn't know exactly which, this ability doesn't really help him at all. Sure he could cycle through all the books he knows, but he'd have to traverse the entire area of his search, changing the book multiple times every time he gets into a new range, and if it's a book he doesn't even know about, he'll still never find it.