Probably nothing yet. It's just now on the table as an API and will take some time before it gets implemented into any apps... especially considering that developers can't even test the feature without a new iPhone in hand.
Does anyone have a picture of the gyroscope though? Like a teardown (I saw the iFix it and I want something that shows me the actual component) of it or something similar? I'm just trying to wrap my head around how it actually works... literally a spinning disc inside?