The first thing
you should always do is figure out what you are trying to do. for example:
What would the thresholds be? Will they need to change throughout the day?
How do you want to be alerted - email? phone call? pop-up window somewhere?
Don't write a single line of code until you think through these at minimum.
There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors