The event feature does currently not work on Android 8.0 or newer versions.

Download the app to get your unique Simplepush key.
There is no registration required.
After your free 7-day trial the app will require a one-time $3.99 in-app purchase.
Use your Simplepush key to send notifications to your device.
Sending a push notification to your device is as simple as a HTTP request.
You can customize ringtones and vibrations for your notifications with the Events feature.
End-to-end encryption can be used for increased security.