Looking for Feedback on a Devops Idea

Hey guys, we have built an internal server agent (a nodejs based service) to create a few checks and balances on our servers. For example, if any of your services are down like Cassandra, Mongo or checking if any of your ports are open or checking on APIs if they are accessible for non-logged in users, etc. We are thinking to make an open-source agent for servers which can check for you such things. It will be extremely simple to use and will charge only for API calls above a certain number or so. What do you guys think of this idea? Is there something similar in the market which is simple and extremely cheap? Would be extremely useful to know your thoughts on this?