Facial control via your iphone X for controlling synth or effects parameters.  Pretty cool.
What CC# is my amp attack env?  Oh wait just stick my tongue out more.
My left nostril does a great half cocked wah.
 
BandLab is prime for that sort of innovation too.
 
full release notes for GarageBand for iOS version 2.3.3:

• New downloadable "Toy Box" sound pack with free educational sound effects, including animals, vehicles, and counting to ten in different languages.
• Use facial expressions and the TrueDepth camera for hands-free control over musical effects like guitar wah and synth parameters*
• Adds Modern Wah guitar stompbox effect
• Provides stability improvements and bug fixes

* Apple's fine print: "Requires iPhone X. GarageBand uses ARKit face tracking features to translate your facial expressions into instrument effect controls. Your face information is processed on device, and only music is captured during your performance."