[tesseract]

More likely a hall effect sensor, which is solid state and a lot smaller. And yes, older MacBooks had something like that, as evidenced by the fact you could put them to sleep by holding a magnet in the right place (just to the left of the trackpad IIRC in the models I'm familiar with)

[0_____0]

I pranked a coworker once by sticking a magnet to his desk somehow to get his macbook to sleep when his computer was in a certain spot.

[rafaelmn]

Nice one ! Curious since I know almost nothing about HW - do magnets screw with computer HW otherwise ? I would guess no since we don't use HDD anymore but not sure.