Also keep in mind that depending how frequently you poll the endpoint Barry suggested you could end up getting one response saying a stream is online, then the next time get an offline response because you just happened to hit a slightly older cache.
So you might want to make sure you don’t poll too frequently, or set up a counter so that once a stream is live it only gets set as offline if you receive x consecutive offline responses from the API (a counter like this can also help if a stream is having connection issues and is going and down a lot, as an app can still count it as a single broadcast unless it’s down for an extended period of time).