I am aware if it is possible to wake up an app when the user is close it a beacon. It know it is possible to do it on iOS. I have not found a clear solution on the web. Do you know if it is possible?
Yes, it is possible with the open source Android Beacon Library. It works by starting a low-power background beacon scanning service for your app when the phone boots, or when it is connected/disconnected from power.
Details about how you set this up, how it works, and its limitations are available here.