Just as important as testing an API before and after release, is validating that API is always up and functioning as expected. This is the difference between Uptime (which an APM can measure) and Functional Uptime, which is a powerful and unique aspect of API Fortress.
Ultimately, it means using your existing detailed functional/integration tests, and scheduling them to run against a live environment. This way they are constantly testing for uptime, functionality, and performance. The details on using the scheduler are here, but there are some important notes.
Note 1: A test must be Published before you can schedule it. This allows for there to be a finalized version that doesn’t get affected when you start editing a test. This is because when you edit a test it creates a Working Copy.
Note 2: You should monitor your own APIs, but you can also monitor third party APIs! Have a partner API with an SLA? Make sure that API is working as contractually agreed upon.