BLE

BLE is a protocol that is commonly used for devices that collect data, and share it with a bluetooth device like your phone.Devices that support Bluetooth 4.0 will also support BLE, this includes many modern smart phones.

On linux computers, the tool gatttool can be used to interact with BLE devices.

Use
I suspect that some devices may used an extended version of BLE to interact with their devices. I have been able to make some heart rate monitors ike the xioami Mi band pair using BLE, and collect metadata abut them. But have not been able to get them to switch on.

Some scales use BLE and have been reversed engineer.