Another example. On our woodworking machining center (not mach3 though), there are 4 different zones with pop up pins to locate your parts. You place your part in the correct zone, step on a foot pedal to activate vacuum, and push a start button to run your parts. The machine is homed once a day when turned on, and that's it. We run several hundred unique parts a day, and it only takes seconds to load the program (with barcode scanner), place the part and start running.
I'll be using a similar system on the router I'm currently designing. Home to switches, and have 0,0 offset form the switches (X,Y) by 2-3 inches. Most parts will be placed at 0,0 (via some type of fence or stop system, not designed yet) and run. No need to zero the tool to run parts.