How to capture motion with magnetic sensor?

Hey there,

Purpose:
I want to design and build a basic system that detects human movement using magnetic sensors. These sensor will be attached to the human body.

The problem that i have is that i dont understand how to build this system. I understand that you must have a magnetic sensor (Any suggests on which would be helpful) that connects to a transmitter (again any information would be nice) that is then connected to the PC, where a software package will convert the signals from the transmitter into useful information.

So a basic overall of the structue is:

Sensor (Detects movement) ------> Transmitter ------>PC

Any ideas on how this could be acheived? also at low cost.

Thanks for your help in advance.

Rich