@blynk_app I have a hard time to find a concrete answer for this: Can I use a with Blynk designed Android-app to control a NodeMCU without using wifi nor any form of internet-connection? I only want to connect through Bluetooth to the NodeMCU. Will it work without "cloud"?

Bluetooth is in Beta, you can try. Some people are successful with that. However, Blynk was designed for the -=Internet=- of Things, where Internet is the key word.

Well, aside from this one project my goal is to keep the IoT-devices local. I don't want my devices to communicate with 3rd party servers.