First, some stuff to look at:
But yeah, this thing is just a ghetto DIY slip ring made of pogo pins, a selector switch from a resistance substitution box, a nixie power supply and a Burroughs 122P244 nixie tube (with bonus Krypton 85 inside).
I actually remembered to take photos while I was doing this, so you get to see the quick n' dirty nonsense that went into it.
And here's how long it runs off a little battery
This topic is very nice