Is it possible to connect miband2 and arduino nano (?) I want to make an IOT project using an Arduino nano and I need heart rate sensors. I I have a miband2. So, is it possible to connect them ?
You need to connect as a central device.
I've had good luck with the adafruit nrf52 feather.  Also see: https://github.com/Freeyourgadget/Gadgetbridge for the protocol.