It looks like an aftermarket GPS tracking device. "This side up" is the giveaway. If you don't know what it is and don't use it I would follow the wires up and remove it. Someone is watching you and keeping tabs on you for sure. Google the numbers on the white sticker.
Tracking Device Found in Customer's Car! - YouTube
It's likely a financed or leased vehicle that is being tracked. Very common these days.