I was thinking about my Garmin bike computer. It apparently has audible alerts, but I've never heard them. Same with a heart monitor watch. You get a beep when you hit a certain heart rate, apparently. At least the phone gives you a range of ring tones.
As for hearing aides, I have a serious case of tinnitus along with high frequency hearing loss which is not helped by amplification. The constant ringing in my ears is the loudest thing I hear. Fortunately, I've learned to ignore it. It drives some folks nuts!
I figured my older friends would empathize.