thanx for the provided link, but for some reason, this solution did not work for me at all.
However, after a while of trial and error, I found a formula that does the trick for me. I know, it's far from perfect, and I have to admit - I don't even quite know what I'm doing here - but the results are quite satisfying for me.
(floor(clamp(((accelerometerY())*80), -560, 570)/(2*pi))) I get values from -90 to +90. (used for the background)
Update: After I just learned, that accelerometerY() outputs -10 to +10
(floor(clamp(((accelerometerY())*9), -90, 90))) should translate the output in degrees directly. (used for the glare).
You decide which rotational rate you like more, as these two formulas produce different accelerations, but equal maximum values.
Here is a quick mockup if you wanna see the outcome: