This change in Google Play Policy from 23rd Aug 2013 means that push notification from the outside sources are not allowed any more, only from within the app. You may send your users notifications on your own, it is only that third party ads through push are forbidden. That is why tapcontext say that you should show the interstitial ads first when the app loads and that you should also send notifications of type “here is a new feature, please take a look” or “you probably did not know that my app can do this too”. The goal is to motivate the user in an ethical way to run your app, which will then show your ad as soon as the app opens up.
Which means that we shall have to make our own push notification queues for each app, turning our apps into an aweber of a sorts. So, if you want money from free apps on Android, the production of an app does not stop with creating the internal content of the app, you will have to write the auto responder notification sequences too.
Currently, you will have to send the push notifications manually, although with some PHP code it should be possible to create the sequence in advance.
This also shows the difference between a site and an app. In a site, you have to lure the user to leave his or her email address, with an app, you automatically have the ability to send push notifications, no bait needed once they download the app.
If you can lure the app user into giving you their email addresses, so much the better. This may seem easier than it is. You may show them the Email Us plugin first but it is a bit more complex than that. The user should be able to bypass giving you the email, and once the user enters the email address, you should not show the prompt any more.