StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Spotify - Map shows when two people play same song at same time
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.
Playlist Machinery - Tools that help you create & organize your Spotify playlists
UptimeRobot - Free Website Uptime Monitoring
Magic Playlist - Get the playlist of your dreams based on a song