APIs are like websites: they are available most of the time, but unfortunately not all the time. WatchMouse is a global industry leader in website and application performance monitoring. WatchMouse API and web services (cloud) monitoring checks the availability and performance of APIs and web services. Using the its scripting technology the full flow of almost all APIs can be simulated and replayed periodically.
http://api-status.com/ is an example of a site that is powered by WatchMouse API & web services (cloud) monitoring. Each of the entries on this site is updated with a WatchMouse scripting monitor that behaves as a client for these APIs.