I have found that the speed of the metronome is not correct vs. a stopwatch or other metronome devices. The metronome runs too slow, making values found with the tap function too high.
My tablet is a Samsung SM-T810 with Android 7.0
If such issues can't be dealt with globally, it would be nice to have a calibrating option.
At the moment, I'm relying upon Google's AudioTrack class to play back the sound effects for the metronome. In practice, I've found the playback latency to be acceptable on most of my devices. When I use a different metronome app on my phone, for example, and play it back at the same time as the metronome in MobileSheetsPro (running on a tablet), the two stay in sync the entire time. Having said that, I know that audio latency is a big issue on Android and the performance can vary drastically between different devices. It can also be affected by other processing that is occurring (such as the heavy processing involved when rendering pages in MobileSheetsPro).
Pretty soon, I'm going to be making changes to the AudioPlayer to use a different backend that supports changing the pitch and playback speed. The same framework I use for that claims it has solved the Android audio latency issue. As part of this work, I will also try to switch over the metronome to that framework. This may solve the audio playback issues on devices that currently don't work as well. I would prefer to wait and see if this fixes the issues you are seeing before adding something like a calibration option.
Thanks,
Mike