Growl for Windows - Growl for Windows is a Windows-compatible version of https://alternativeto.
Netumo - Ensure healthy website performance, uptime, and free from vulnerabilities. Automatic checks for SSL Certificates, domains and monitor issues with your websites all from one console and get instant notifications on any issues.
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
AppZero - AppZero is a monitoring and migration tool that allows users to keep track of different applications and servers in both simple and complex IT environments.
Notifu - Notifu, a free open source pop-up balloon utility
RedGate SQL Monitor - SQL Monitor helps you and your team find issues – before they become problems