Bluetooth Low Energy - Over-the-Air Update (short BLE OTA) is a project, which can be used on ESP32 (and maybe later also on STM32) to update the firmwares. It contains of two parts. The first one is a mobile app, which checks for new firmware and sends it to the devices. The next iteration of the project will include a backend server, where the firmwares are stored, so the app doesn't need the files locally.