Well I have seen pressure guages on a couple of customers units... I myself have never used one and I personally don't believe you need one. The best way to set a system up is to add pressure until you have an nice full fan and your wand does not kick up hard wehn you pull the trigger.
As for meters for the units i have seen one once on a unit from bellvile and they said it worked ok. Meters are a tough think because they are never exact and I don't have a source for them.