Fun idea! One thing though, I'm not sure about showing the donated amounts and totals behind each speaker, while they're all on stage. It could quite easily lead to a very distracting and embarrassing situation if they weren't zapped equally.

How about instead, you just show the total zapped for all three on top, as well live notifications whenever a new zap happened? If you really want to know the ranking of all speakers, you'd simply have a webpage displaying that information up on a screen outside the speaking rooms (like what you showed on twitter).