Aveo cam sensor question

The Chevy Aveo uses this lil' dude 

bolted to the front of the head reading the backside of the cam gear

Looking at the back of the gears

I don't see what it is triggering off of. 

My question. Is it reading the teeth on the pulleys? Are there magnets imbedded in the gear? Three wires usually means hall sensor so I think I can make it work in my scenario. 

That looks exactly like the cam sensor from my son's 99 Isuzu Rodeo.  I have no idea what triggered it either, and it would run perfectly fine with it unplugged.  

You did not get a photo of the backside of the gear in question, which looks to have four or five spokes.  You got the seven hole one, and a VVT one that isn't on that engine.

Look carefully on the sprocket on the right.  There's a half moon on the outer rim.  You can just make out the half moon on the inner rim 180 out, which is what the sensor is reading.  There's a half moon on both sides so the sprocket is in static balance (or maybe so it can be mounted either way?).  Because the engine doesn't have VVT, it doesn't need to read teeth to know the exact cam position, it just needs to know if the crank is on 1&3 or 4&2.  Or depending on how it's mounted, 3&4 or 2&1.

In the Megasquirt world, I believe this is called a polling sensor.  The computer looks at (polls) the sensor during the missing tooth part of the crank sensor pattern and sees if the cam sensor is high or low.  I think.  Been a while since I set up a half moon.