Firebase: Check for changes in JSON and automatically send notification

UPDATE:

Ok so from all the comments I got convinced that using Firebase is the best solution for a number of reasons but how would I check for that change (canceled == yes) in my json file from firebase and automatically send the notification if the course is canceled.

Sample JSON response:

        {
            "class" : "Class",
            "time" : "00:00",
            "trainer" : "T",
            "canceled" : ""
        },
        {
            "class" : "Class",
            "time" : "00:00",
            "trainer" : "T",
            "canceled" : ""
        }

INITIAL QUESTION

I am parsing a json api and one of the fields is called canceled.

I would like my app to set a notification whenever that canceled key has a value of yes and so far it's easy, just create a simple notification like in the android developer topic and if canceled == yes update the Builder and then notify();.

The issue here is how can I keep checking for changes in the json after the app has been closed and set the notification ?

I have access to the server and make changes to the api if required.

Can I do this without the help of any third party services?