This is the application for your raspberry pi that with a sense-hat added over GPIO will allow you to detect vibrations representing bubbles from your Carboy with the hope that it will help you know when to take your final specific gravity readings for your beer and begin your bottling or kegging process.
This application will also advertise over BLE with the name "BeerBubbler" and some service data to allow it to become discoverable over GATT. It publishes its data on several characteristics.
For ease of use you can find the Android companion application here : Beer Bubbler Android App