None of this is particularly difficult, but OP's explanation of what he's doing brings me back to my original comment about cost!
First, similar systems are already on the market at various price points.
Second, this system needs to be operable by non-technical people. Meaning all the configuration they need to do has to be easy to use and understanding the various options will take time.
To make it useful, someone has to step up and create a wrapper around the existing online IoT server offerings (or create one!) that's oriented towards this use case. That means that "someone" is going to charge, cuz, well, most people don't work for free for long! In the end, the existing SMS system is probably going to look like a good solution.
It's not hard, but it's not going to be cheap either!
Look at it another way, OP. This isn't a project: it's a business opportunity.
wvmarle:
This explanation makes it sound a little easier.Monthly e-mail reports & alarm e-mail when needed is not too hard to implement.