Re: "Create a stethoscope" ... I came across a science fair project where a student built a system that (1) inserts a microphone into a cut-off stethoscope, (2) uses a smartphone to record the sound from said microphone, (3) is accompanied by his software with an AI model that can do some initial analyses of the recorded sound, and (4) packages up everything and sends to a human doctor. We awarded that project first prize for its category.
Re: "Help yourself get to sleep" ... it need not necessarily be playing sounds of "white noise [or] ocean waves [or] crackling fire," it can be set to really boring podcasts, old TV reruns, lectures, sermons, audio books, etc.
Re: "Control your phone with your voice" ... it occurs to me that maybe I use the word "cheese" to trigger the camera "click" function, that way I will be naturally saying "cheese" when taking a selfie. (OK, maybe double it up and use "cheese cheese" as the voice trigger to avoid accidental triggering of the "click" function.)