Help with Magnetic triggers

I have been looking into the solid state triggers as I need to fabricate an ignition pickup for an electronic ignition system
(triggered 4 times per revolution from cranking speed up to 6000rpm). As far as I can tell there are two main types of trigger, one depends on a magnet going past, and another has a magnet in it and relies on a lump of steel/iron going past to cause a pulse (I think this type is called inductive). Some are powered, some just have a coil to give a pulse, and one I have seen has a coil and a powered op-amp chip on board.
I think the Hall Effect ones give a fixed voltage pulse, whereas the coil type give a bigger and bigger voltage the faster they are triggered. Is this correct ?
For ignition I need something fast switching, weatherproof, and ideally triggered by metals rather than magnets - so I was thinking of an ABS sensor from the scrapyard. I don't know if these are Hall effect or not, but they must have the magnet inside. Anyone know ?
Am I on the right track with this, as I haven't found any useful web pages explaining this lot ? I have found I can buy a crank trigger assembly for $300 ( ) - but thats a lot of beer money !
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