Crank Position via Hall Effect

[James W. Swonger]

The magnet on the f'wheel will give a narrower pulse and, with an inductive
pickup, a larger signal. A Hall device will not see a larger amplitude,
just a shorter width. 

The angular precision will be greater for a given magnet diameter as the
radius increases. 

I would look for one of the newer magnet materials (SmCo, NdFeB, etc) 
rather than the ceramic or AlNiCo types. There are pretty amazing
differences in field strength. There are also significant differences
in materials' behavior at higher temperatures, so check that out
before you pick one.