Don't know if this is still relevant, as the question wasn't closed, but for those seeking the answer... there is now a Flutter Sensors package which does all the magic for you.
You'll have to subscribe to the streams to get the current values of the accelerometers and gyroscopes, of course.
For example:
@override
void initState() {
super.initState();
_streamSubscriptions
.add(accelerometerEvents.listen((AccelerometerEvent event) {
setState(() {
_accelerometerValues = <double>[event.x, event.y, event.z];
});
}));
_streamSubscriptions.add(gyroscopeEvents.listen((GyroscopeEvent event) {
setState(() {
_gyroscopeValues = <double>[event.x, event.y, event.z];
});
}));
_streamSubscriptions
.add(userAccelerometerEvents.listen((UserAccelerometerEvent event) {
setState(() {
_userAccelerometerValues = <double>[event.x, event.y, event.z];
});
}));
}