I hooked a bluetooth module JY-MCU to an ESP-01.

This worked after some tries: Getting the RX and TX pins connected/programmed correctly.

The JY-MCU should show up for other bluetooth devices (ie for my computer). However it took 30 minutes until it did that.

After that it was easy as Windows already provides COM port mappings for the device once paired. A connection (on Windows) was done with CoolTerm over the outgoing COM port.

Example code for the ESP (Arduino) side of things is very basic and was taken from https://www.tautvidas.com/blog/2015/12/easy-arduino-bluetooth-communication-with-jy-mcu/