The Cell Phone Tracker
Everyone in this movie is flirting with the dark side, not least of whom the guy who spends all of his time in black. Like Harvey, Batman breaks the rules when he finds it necessary, though unlike Harvey he's very aware and accepting of what he's doing.
His big test comes with the cell phone tracker, a scary surveillance device that lets him hack into any phone in the city. (Seriously, if you thought it was embarrassing that one time your mom spotted those pictures on your cell phone, imagine the freaking Batman taking a gander.)
Like Harvey and the coin, he's using it for the right reasons. Because the Joker really does need to be caught. But again, he's using the ends to justify the means, moving closer to the Joker's way of thinking and embodying a world without rules. So like Harvey and the coin, the tracking device displays Batman's darker side: the side he may really be fighting with and which threatens to overwhelm him in light of the heinosity being perpetrated by Captain Smiley Face. "Beautiful… unethical… dangerous," Lucius Fox remarks, which sums up its seductiveness—and its danger—pretty succinctly.