I don't know if this idea came from my own head or if I briefly read about it on the forums somewhere (probably the latter). But basically, wouldn't it be a lot easier and more accurate to control a PID with a pressure transducer rather than a thermocouple? This would of course only be possible for HX machines, but the advantage over the thermocouple PID setup would be instant recovery when the steam wand opens. It would be an advantage over the pressurestat too because it would eliminate deadband, get rid of the 'click', and be a lot more reliable. I wonder if there are any PID units available on the market that have the ability to process input from a pressure transducer. It would sure make an interesting project. If anyone knows of this already having been done I would love to hear about it.

Some recent discussion here in, Best thermocouple location for PID controlled steam boiler

Alas, no one chimed in that did it yet, except the link to the PDF on the Sean Lennon's Brewtus.

Hmm, I think I've seen that. I never noticed that he used a transducer though, that's pretty cool. I think this would work very well for reliability and precision in control for HX machines (mostly the former). If I had the cash I'd go to work on this. So does someone else want to go through and make some espresso machine history?