#1
Some bands use some kind of metronome system when they are playing shows, I know Thrice does and there are probably a lot more

but I cant find any of these, i found some earpieces but if your whole band were to have seperate earpieces that were not synchronized, then everyones timing would be off, right? I havent tried that but I'm guessing that is what would happen

Basically my question is where do I find a metronome ear piece system for my band to keep perfect timing at live shows

please!!
#2
In Ear Monitors, generally hooked up to a click track. I know Dream Theater uses IEMs, and they all get each other member of the band, but at different volumes. John Petrucci hears everything, James has his vocals loudest, then drums for timing and possibly guitar/keyboard/bass in the background.