I mean, Apple already gives you the option to collect this type of data using Apple Watch and iPhone - if you want it to. One of the most interesting is gait analysis that can warn you if you are getting a bit wobbly and have increased risk of falling. The already do facial scanning for FaceID (held on-device in the Secure Enclave) and offers the ability to scan the shape of your ears to get the best from it's Atmos audio when wearing headphones. There's never been any suggestion that Apple exfiltrates this stuff for any purpose other than those selected by the user.