//final String REGISTRATIONS_ID = "APA91bGgs7g-iF1kEfo_Y5v-iU3IZRW5dODsRLL3nx7YrRy-Y46oUreSMDzUV8KEs61lBjA_GlaEwAN6Mr-kfH_N2kdLtsP2OQsLKr4r9mfweVelaM0u7LC_HsMyRce-F2JaO2wtxFAGXZMlD76pHZ9XEywdIdKhUCvjB5ErO-8Y67lGVICiZb8";
        final String REGISTRATIONS_ID = "APA91bH6pvkDTKnkIw6RvKjjJYk5cV3l7tvGOE8Mkiq8sCoGbOMXSVjs8Kyn40dv8zTzovQuDv4Ub-0xhRavTguqOWxyZCm0nk4Nn1wIfL5nP-xq1cT3j-jbHmKgzjE49KP7Cd0lQ3-mIVHhRPGRukOljOQySCITxXYMyROLbYd8mEM_929aG1I";


        // create JSON request
        // reference: https://developer.android.com/google/gcm/http.html#request
        JSONObject jsonRequest = new JSONObject();
        try {

            // JSON Array of registrations ids (patient's devices)
            // we get registration IDs from database
            JSONArray regIds = new JSONArray();
            regIds.put(REGISTRATIONS_ID);

            // JSON message
            JSONObject message = new JSONObject();
            message.put("notification", "1");
            message.put("action", "out_of_bounds");

            // put into JSON request
            jsonRequest.put("registration_ids", regIds);
            jsonRequest.put("data", message);
        }  catch (JSONException e) {
            e.printStackTrace();
        }

        System.out.println(jsonRequest.toString());
        System.out.println();

        // Send
        GCMSender gcm = new GCMSender();

        String response = gcm.send(jsonRequest);

        System.out.println(gcm.getStatusCode());
        System.out.println(response);