** Edit: I'm going to backpedal on this statement. See my post below. "Unarmed attack" and "unarmed strike" are not equivalent statements.
Going by a strict reading of the rules, this is not true. Gauntlets and unarmed strikes are both listed as simple weapons. But monks are not proficient with simple weapons. Going by a strict reading, then, not only are monks not proficient with gauntlets, they aren't proficient with unarmed strikes! Poor monks, not only do they have a crappy BAB progression, they also get a -4 to all attacks made unarmed.

Wizards also have this problem.