[AMSAT-BB] Accelerometer/magnetometer in Android smartphone apps

It's time for me to upgrade phones, and I have a question...

I notice that the HamGPS app tells me my phone has an accelerometer, but no magnetometer; lack of the latter doesn't seem to have impacted the accuracy of the app though.

I use AMSATDroid, Heavens Above, and ISS Detector apps for tracking the birds, so my question is how necessary are these two sensors for getting accurate results from these 3 apps (and others)?

In other words, do I need to look for a phone which has both sensors, just one of these, or does it matter?

Thanks

Philip N4HF