For those seeking an API to get streaming information for TV shows and movies along with notifications for new arrivals and departures, several options are worth considering:
TMDb (The Movie Database) API: TMDb provides extensive data on movies and TV shows, including metadata, streaming availability, images, and more. While TMDb itself might not directly provide alerts for upcoming or leaving content, it can be integrated with other services or custom scripts to create such notifications.
JustWatch API: JustWatch offers a comprehensive API that lists streaming content across multiple platforms. It provides access to information on where content is available to stream and can include notification services for content updates and availability changes.
Reelgood API: Reelgood has an API that covers streaming availability from various services. It includes notifications for new content added to streaming platforms, making it useful for those looking to track when content is coming to or leaving different services.
Guidebox API: While Guidebox was acquired and integrated into other services, its features were known for providing detailed information on where content was available and changes in library content. Those looking for this capability might investigate its current iterations or usage through partnerships.
Trakt API: While mostly a social platform for tracking what you watch, Trakt also offers integration capabilities that might, through third-party applications, provide insights into streaming availability changes.

Each of these APIs requires registering for API keys and may have usage limits based on their respective plans, so developers should carefully review documentation and terms of service when deciding which API best suits their needs. Custom implementations can enhance the basic data with specific alerts tailored to your interests or platform usage.