I recently met with some sales guys from a company called Keyence. They make photoeye’s and barcode readers, laser sensors and stuff like that. There was a gauge in their toy box that caught my eye. It’s a gauge that can measure down to .01psi it will also measure vacuum. It has adjustable set-points and has the ability to turn on relays and such. The display will change from green to red or red to green when the output is active. It can also operate as a window switch.