SongUpdater

Song Updater is the best way to follow your favorite Spotify public playlists and get notified when new songs added to them. Now you can stay up-to-date on newly added songs, and add the ones you like to your own personal playlist for your wedding, birthday party, baby shower, etc.
WHAT'S NEEDED
• Spotify app MUST be installed on your phone in order to use this app
FEATURES
• Search for playlists
• Watch or Unwatch a playlist
• View and play new songs added to the playlists you're watching
• Update settings that suits your need
• Send feedback right from the application
NOTE
• This application is completely free to use.
• You can only watch or un-watch public playlists. If you can't see a playlist that you don't own on Spotify, you won't see it on Song Updater.
• No support for Apple music at the moment but hopefully sometime in the future.