API Monitor is described as 'Windows program that lets you monitor and control API calls made by applications and services. Its a powerful tool for seeing how applications and services work or for tracking down problems that you have in your own applications' and is a process monitoring tool in the development category. There are more than 10 alternatives to API Monitor for a variety of platforms, including Linux, Windows, Mac, Android and BSD apps. The best API Monitor alternative is Process Monitor, which is free. Other great apps like API Monitor are Valgrind, Stratoshark, SpyStudio and WinAPIOverride.
Only monitors (some) system calls, not win32 APIs.