Not even Harry Potter's invisibility cloak can shield him from the gaze of Luna Lovegood's Spectraspecs. After all, Wrackspurts don't care whether or not you're invisible - they just want your brains!
Not only can Luna's Spectraspecs reveal the presence of magical creatures, they are essential to participation in Dumbledore's Army. If you want to help overthrow He Who Must Not Be Named, get a pair, grab a Quibbler, and ignore the gits who complain about them looking funny. They're probably working for You Know Who!