Sorry to follow up to my own follow up, but I think I've figured out more.

It looks like I hook up a button/contact block. I like the look of this
one:

http://web4.automationdirect.com/adc/Shopping/Catalog/Pushbuttons_-z-_Switches_-z-_Indicators/Eaton_Cutler-Hammer_22mm_(E22_Series)/Emergency_Stop_-z-_Mushroom_Pushbuttons_-a-_Stations/E22JLB2N8B

That's an "N.C." which I presume stands for "Normally closed." So, when
you push it, it opens a circuit (briefly? Until it's pulled back out or
released some other way?)

That circuit is then hooked up to - what? A relay, I guess, but is
there a special name for it? Or do I just get a 30A relay someplace?
And what voltage (and AC or DC) do I run the contact blocks at?

If I figure it out on my own, I'll followup here...

-BAT