Detect H field from magnet?

[mvdswaluw]

How about a magnetometer? The folks from the SAM project use very sensitive ones that can detect changes in the nanotesla scale:
[/url][url=http://www.speakesensors.com/products.htm]http://www.speakesensors.com/products.htm

My first experiments I did with an HMC5883L IC hooked up to an Arduino. The sensitivity is a bit poor. I can get a proper detection from about 30cm when I do oversampling and take moving averages over a long and short term. At that distance I get about 3-10 milligauss (1000nTesla) deltas . At about 10cm one of the three axis already saturates, so 12bit is not enough dynamic range for me.
 
I've already looked into fluxgate magnetometers, but have not tried it yet. I've seen graphs where people can detected 0.5 milligauss variations at a level of around 500 milligauss.
My next experiments? I think I'll try to build a small magnetometer (smaller version of this) and hook up a 16bit A/D-converter to that and feed that into an Arduino.