Numerical Data from any iOS API

I'm looking for any iOS Library that supplies numerical data.

My menus show a few animated graphs in the background, right now I use mostly random data. Now I'm looking for any kind of dynamic data one can read from the iOS Api, be creative, what would you use?

1. Obviously I already use the Accelerometer input


2. FFT of Mic input is an option, but then the user will get the "Allow this app access to the microphone" which would be weird because I don't use the mic anywhere else

EDIT: Also performance should not exceed 5% of cpu load. Right now with my random data I use BLAS so it really doesn't affect the rest of the app. It's just for aesthetic sugar.