Sorry, R1 and R2 are labelled backwards as compared to your circuit.
Note that depending on the comparator (and especially if you're using an op-amp as a comparator), the input voltage range may not extend to the negative rail. In the case of the one shown above (the TLC3702) it does.
Having a regulated 12V source would allow this to be more stable... and would prevent the alarm from triggering on a false positive from the 12V source drifting. This of course will depend on what kind of accuracy the OP wants.
Alternatively, does anyone have any objections to using a diode on the + side of that Comparator?
You would need to feed the output from the Aneamoter to a voltage divider, but that would ensure a more stable reference voltage would it not?
Alright, looks good I'll breadboard this and play around with it. I still have to put together a 12 vdc voltage regulator, maybe an LM7812. Thanks again Dan and everybody else you all have been really helpful.