Any schematics or information on making a EStop

I'm building my CNC machine and now I need help in a design to use
for a EStop. I'm using Mach2 and Axxus indexer card with some IMS483
drivers. I have no idea were to begin or where to obtain the actual
stop button. I would like to be able to hit the button and kill the
hardware as well as inform the software I did this. Mach2 has the
setup for this and the indexer has the pin out for it, I just need
help in the design phase and were to get the button.

Any help is appricated.

Thanks,

Shawn