A free app for Android, by Nordic Semiconductor ASA.

nRF Connect for Mobile app allows you to scan, advertise, and explore your Bluetooth Low Energy (BLE) devices and communicate with them.

It is designed to be used in Android devices and supports number of Bluetooth SIG adopted profiles together with the Device Firmware Update profile (DFU) from Nordic Semiconductors and Mcu Manager on Zephyr and Mynewt.

The tool parses advertisement data and presents RSSI graph from your BLE devices to help you make informed decisions. Plus, it lets you read and write characteristics for a more precise handling of your devices.