Question about E-Hogu - Taekwondo Electronics Chest Protectors

Hi all, i'm new to Arduino and I have some questions for you. :)

I play Taekwondo and after many researches, I need advices for my project.

I would like to know how electronics chest protectors works, I read on forums they are made of piezoelectrics sensors.

So my first question is, which kind of piezoelectrics sensors ? Ceramics, Velostat ?

Which choice would works best ? I want to detect a foot impact on the chest protector and mesure approximatively the force of it.

[u]How many piezo elements I need to cover the whole surface of the hogu[/u] ?

PS : Sorry for my English, I do my best. :D

If you do a Google search for "Taekwondo piezo", the first (non advertisement) result explains the system used at the last Olympics.

http://www.meas-spec.com/news/PiezoFilm/Taekwondo_PiezoCable.aspx?menu_id=546&tax_id=128

Many thanks mikb55 !

Piezo Spiral Wrapped Coaxial Cable, what a great idea !!! :)