I think there’s a wide spectrum of senses one could attribute to wizards, widely ranging in power, and from the whimsical to the more practical.
If we’re aiming for something closer to the dwarf’s senses, then it’s more the pragmatic, procedural side of things. Something that slots into the usual dungeon exploration. It’s easy to get something either too useful or useless here. For example, if we’re being rather “dwarf-like” and give the MU an ability to detect if a certain part of the dungeon was made by magical means, does that come into play often enough?
“Is a magical creature behind this closed door?” might be too good, especially if it works all the time.
Something like “knows when other creatures are spellcasters” sounds okay enough to me. It has some tactical and role-playing benefits, but isn’t really unbalancing in general. Quite often you’ll find that out soon enough… But you get this Highlander sense that has a certain appeal to players, and it creates some “connective tissue” between you and other casters. I wouldn’t restrict it to arcane casters, though. Both for simplicity’s sake, and it would be quite cool for worlds where there’s some antagonism and warlocks/witches could suss out priests that might hunt them.
On the more setting-specific side of things, what about being able to know the positions of the stars at all times? Quite a few backgrounds have that as the source of arcane magic. For RP, you can do your horoscope from everywhere. On the practical side, it’s basically an extended direction sense, although one might require the MU to actively concentrate on it.
One could have something that gets more powerful as the MU progresses, although it might be fun to not tie that to mere levels.
What if you have some very basic ability, but it gets better if you get proper MU attire? Wizard’s hat, robe & staff (the MU might start out with simulacra, but you only get a boost if it’s proper)
Or maybe ioun stones? With none, you can touch something potentially magical and after a turn of concentration you know whether it really has the arcane spark, but if you’ve got nine ioun stones floating around your head, you basically see the matrix.