anyone know how to make a boost gauge?

[stackz]

I've already figured out how to make an electronic boost controller heh. I built one myself that I can control from inside the car and all and tested it on a friend's car since my turbo kit is still on the way...

What I'm wanting to do is build a control box for it and have a digital or analog boost meter (doesn't matter as I've already designed layouts for both types) What I'm wondering is this...does anyone here know the theory behind boost gauges?? do they operate on a diaphram type setup?? how do the digital one's measure boost?? are there any do-it-yourself guides on the internet on how to build a functional boost gauge??

hell I think my little "invention" works awesome...my friend has demanded I build one for him but that's besides the point hahaha

I'm just wanting to make everything (control of boost) and (reading of boost level) in one package is all...I know I could go with my analog design and just literally buy an aftermarket mechanical boost gauge and toss in it but I'd much rather have the slimmed down look of the aftermarket boost controller/gauge setups and all...

please help if you can, I've been searching the net for the past four days and can't find shit heh....and yes, I'm too cheap to tear apart a perfectly good boost gauge especially when I'm not trying to use an analog setup if I don't have to :

[LOW DID]

the digital ones take the signal off the ecu or map sensor that shows manifold pressure.
and to make one, that seems really ghetto, why not just buy one from a junkyard that was on a factory turbo'd car for like 5$?