Re: This leaves open all sorts of pranks!
"I'm not sure you'd get past the x-ray machines if your hand luggage included a small circuit board with wires attached to a small solid looking object such as a battery."
You never know. I came from the US into Australia, with an 16bit ISA card, along with cables, and they didn't bat an eyelid.
Yet, I've had friends bring in hard-to-get spark plugs, and power transformers, and nearly had the feds called in.
Do not underestimate stupid. If you think you need enough brain cells to sucessfully breath air, look at some of the TSA agents or whoever has been empowered to decide if you're a terrorist, or a bratty kid. I doubt they can tell the difference.