I have been working on improving my earthquake prediction device and I am adding a MMA7361 Triple Axis Accelerometer - motion detector too.
The recent changes include changing the UGN3503's to be differential inputs to the op amps. This gives twice the output swing per change in magnetic field. Using a digital VOM it is now .1 volts for a North to South reversal. That translates to about 20 on the Arduino serial data stream.
This change reduces the inputs to the Arduino to N-S, E-W and U-D, or three inputs. The other three inputs will come from the MMA7361. I am still working on getting that working.
Here are pictures of the MMA7361 board being tested on a Arduino Shield. The wiring is very simple to do.