I need to count and display wheel turns (Magnetic sensor)

Hey guys, I need to make a little something with a magnectic sensor attached to a frame and a magnet attached to a wheel.

Everytime the wheel turns a whole 360 degres, it must display the incrementing value on a display, like a LED display or something.

I was thinking of using an arduino with a sheild and stuff but it'll be like 50+$

Any idea how to do that with basic components ?
I beleive I did something similar a long time ago at school and required a simple OP AMP and we were changing the bits with a push-button. Now, it's a little bit far back but I'm sure I can increment bits with a magnetic sensor and whatnot

May you enlight me

oh and if it helps, I would like to use something like this:
**broken link removed**
it combines the display and an AtMega328

Buy an **broken link removed**, or hack a pedometer.

Wow this is great !

I figure it is possible to replace the switch by a magnetic sensor in order to avoid a physical contact ?

Simple cut+solder ?