Data transfer without WiFi

[Physikator]

I wanted to measure the pressure in a closed metal lunch box, so WiFi did not work. I managed to create an experiment to generate a sine wave with a frequency corresponding to the air pressure, 1hPa=1Hz. With a second phone I was able do receive the sound and show the frequency=pressure over time. However, this is not very reliable, other sounds disturb the measurement. So I thought of using the vibration alarm as a signal source and a magnetometer as a receiver.
Does anyone know if the vibration generates (enough of) a magnetic field for this to work? And might there be a way to activate the vibration via phyphox?
Thanks a lot!