I received this set in the mail last week:
http://doc.3dmodularsystems.com/ps_on-kit-assembly/
and started building it into the base of my RMaxV2. May main goal was to be able to shut down after a print, and to create protection against fire. It all fits without problems, next to the bed SSR, 24V PSU and 12V stepdown

But while I am busy with it, I am thinking if this is the right approach. The idea is to hold the pushbutton a few seconds, until the PS_ON signal is up an closes the SSR so you can let go of the button. It is also possible, I think, to power the duet (0.6) through the USB connector, and have the possibility to power ON through the GUI as well as OFF. I would have a "main" switch as well to power down the electronics (and open the SSR as well).
What is wise, what would you do?
I am also planning to put one or two NC temp fuses in series on the PS_ON chain, so if one fails the machine stops. I think a 150C fuse would suffice to prevent hazardous temps to start a fire. One against the bed and one on the PSU housing, but the PSU probably is already heat-protected, have to check that.
I am DeltaCon, I have a delta, my name is Con, I am definitely PRO delta!

Rostock V2 / E3D Volcano / FSR kit / Duet 0.6
PS.: Sorry for the avatar, that's my other hobby!