Real-time developer notifications allow us to monitor state changes for Play-managed subscriptions (canceled, renewed, purchased etc.) on server-side. What I want to achieve is the same but with one-time purchases. So getting notified when someone purchases, but I can't find any info how is it possible.
Other option would be using a cron job and checking the last purchased items regularly, but I also can't find any endpoint for listing these items.
Someone any idea?
An API for this doesn't exist, and to be honest is unlikely to ever be introduced. You can see why if you think for a minute about popular apps. According to this article Supercell made 1.6 Billion dollars in 2018. Assume half of this came from Android (I don't know the real numbers).
And assume it mostly came from $1 in app purchases (I don't know the real numbers).
Then there were 800,000,000 purchase events in 2018, or 2,200,000 per day, or 90,000 per hour or 25 per second, and that is from a single developer. The number of calls to such an API would be huge, without giving much user benefit.
If you are just curious about how your app is doing, can I recommend the official Play Console app?