Vacuum shift light

[Samtech]

I posted this over on Pelician but those guys didnt really understand what I was
asking about, just some fodder about how I must not be holding the gas down or that I should get a rpm shift light... Which I have...

So how would one go about adding such a thing?
It seems to me that running out of breath and hitting the redline are two different things.
Check out this video;
http://youtu.be/Yj4-clpN8N4

So on a turbo car would you want a vacuum switch between the airfilter and the turbo inlet set to 1-5 inches or a pressure switch on the manifold set to close at anything below max boost pressure?
I can deal with the light being on while I'm not on it but how do I get that soft glow and modulation?