Would you pay a modest fee (say $5 a month) for a service like this that sends text and/or email alerts with important information, including the ability to monitor specific address(es)?
Whenever you respond to a request for a product or service and ask if the requester would be willing to pay for said product or service, the answer is almost always "no".
I call that: The Goodnews Everybody Universal Law of Technological Entitlement.