I was looking around for weight sensors that would work with arduino, and found this http://www.seeedstudio.com/depot/weight-sensor-load-cell-0500g-p-525.html
Just thought 17$ was a bit expensive, so I started looking for something else that would do, and found this http://www.dealextreme.com/details.dx/sku.35716
Inside I found something looking a lot like the first sensor, just mounted on a nice metal bracket, perfect for modding without having to build the entire thing to hold the weight.
My problem now is just that I got no idea of how to actually use such a sensor.