Here is bluetooth communication between the RPiSoC and an Android phone. Imagine all the things you want to control in your house without actually walking up to them.

I send a string of text from the phone to the RPiSoC, which then displays it on screen. We used the JY-MCU bluetooth module for this, because of how cheap ($6) and well known it is. An Arduino shield would have worked, but is overkill (and I wanted to use the screen instead) for this. While I couldn’t make room for the HC-05 chip to be directly soldered on, it is quite sturdy plugged in as pictured. You could also plug it into the Pmod headers on the side of the RPiSoC if you want to save vertical space.