An emergency stop is a life safety device.
Yet all too often i see products being sold that use nothing more than a cheap light switch. i have had light switches fail in my house and i certainly wouldn't gamble my life on the chances of a light switch never failing.

This video shows the inner workings of a true emergency stop. Self monitored contacts ensure that it still opens the safety circuit when broken. Copy and paste the link. let me know what you think.

https://www.youtube.com/watch?v=mCUvNvmaRN0