From the looks of it, I think it might be the camera that hovers above the field, it moves up and down and sideways along wires.
edit: I just watched the replay on HD here at my home and that's exactly what I think it is. The two bumps at the top of the moving object are the wheels for the pulley.
I'm pretty sure it follows the movement of the pack of players as they go downfield, above the QB.
If not...animal strays are no stranger to sports stadium.
Could well be a resident cat that the field crew 'adopted' or something to that effect.
edit on 12/12/10 by Tharsis because: (no reason given)