I agree. :-)

I think the first step is to switch the code to use the new sensor API instead 
of using the raw sensor values. We should be able to get the roll, pitch, and 
yaw directly from the API. Then using the gyro should be much easier.

The filtering is a whole other issue. :-) We did a lot of experiments back in 
the day and tried multiple filters. The filter we are currently using was the 
best at the time, but I think its a bit too jittery on modern devices. I'm 
pretty sure that I can dig up the other filtering code to try again. It was way 
less jittery, but a lot slower. The right answer might be to add a setting 
somewhere where the user can adjust the sensitivity. I don't want to overwhelm 
the users, though.

There are kalman filters for Gyro+Accelerometer+Magnetometer as far as I know 
but..   somebody rather knowledgeable would be needed to get on board for this.

Memsense Kalman Filter (no source though)
http://www.memsense.com/index.php/Product-Pages/kalman-filter-library.html

ICS already implements a Kalman Filter if an Gyro-Sensor is available. At least 
on the Nexus S. Just use Sensor.TYPE_ROTATION_VECTOR.

Hey all, I'm learning android development and decided it would be fun to try to 
hack in gyroscope support to SkyMap. I decided to ultimately use the 
ROTATION_VECTOR sensor, which should implement a fused 
accelerometer/magnetometer/gyroscope on ICS and later (though I think it might 
be manufacturer-specific). Testing it on my samsung jellybean phone it works 
really well though, with a fast, smooth response.

There's a new option in preferences to switch between it and the original 
sensor, and it should fall back to the original sensors when ROTATION_VECTOR is 
not available (pre-gingerbread).

Patch is attached. You can download the debug-signed apk at 
http://nullidea.org/Stardroid-debug.apk (you'll have to uninstall the old 
SkyMap first) -- enjoy!

Ugh... except in my apk, all the stars and constellations are mislabeled. Is 
there something wrong with the published code?

Oh lol apparently the star database uses hard-coded offsets into the string 
resource or something. So when I added a new string it offset everything by 
one. Here's a new patch that puts the new string at the end so you don't have 
to re-compile the star binary files (which I haven't really figured out how to 
do). I also uploaded the fixed apk to the URL above.

Tested the patch on an older Huawei phone (2.3.X), after some testing it seems 
to marginally improve things. Much more important though is to set sensor speed 
to fast.

On a moto-g the "fused" option is unavailable.