Very low power magnetic sensor

[mmfuria]

Hi,

I'm looking for a magnetic field sensor (on-off) with very low power comsumption. The Hall sensors I've seen use some current to bias the device and so are not suitable. The low power hall devices switch internally this current, so suffer from maximum frequency of operation. Somebody can suggest an interesting device or technique?

MMFuria

 

[flatulent]

coil

How about an inductive coil going to a comparator possibly with gain. These coils are used for hearing aid pickups and for short range communications.