Second control source for pump controller

[boogalou]

Any ideas or info concerning what to use along with boost to control the amount of injection via a pump controller?

I think a output from a IAT sensor would closely parallel the boost output. So, the intake temp would rise at around the same rate as the boost pressure.

Using RPM as the second source pretty much do the same thing?

Also thinking about voltage output from a MAF....

Or, is a second control source even necessary?

In other words, what other input to a progressive pump controller besides boost do you think would work the best?