AT LEAST one constant is missing from the PhoneSensors library: TYPE_STEP_COUNTER (int 19).
This created a problem for me; I developed an app very differently than I intended, and the app itself was much less useful ("luckily," the app was just for myself).
The point is that only the constant (and others?) is missing, the features are there!
Do you really think I don't know this (I preferred to create the constant myself and use this one)?
The point is that since I couldn't find the constant among the available ones, I assumed there wasn't even a way to use that type of sensor with that library and that's "serious."