Style chooser

That day I saw a product on sale in some accesory shop, the FAKE BOV Sound Maker...
about the price of RM200. I remember Johnson Lam once written a thread on how to do that, some sort like connecting Car horn, sound recording key chain, and amplifier.

Have anyone done that before? Anyone still remember how to do it? And those sound recording key chain. Where to get them? I used to have one when I'm small.. but these days hardly see them around.