Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
Microsoft Research Detours - Detours is a software package for re-routing Win32 APIs underneath applications.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
WinAPIOverride - WinAPIOverride : This software allows you to monitor and/or modify any function of a process for any calling convention (stdcall or cdecl)
Better Uptime - We call you when your website goes down
EasyHook - The reinvention of Windows API Hooking