I had this idea, kinda. I didn’t consider Morse code. And, I didn’t consider the vibrate motor.
When I get a phone notification, usually I just need to know which app it was. (Ok, actually sometimes I want to know app+user. The following could be extended to that, but I’ll drop it for now.)
So, to assign a unique, easily recognizable tone to each app-name, I imagined (only, never tried to implement) a mechanism that takes each app name and hashes it to small integer–about 12 bits.
Then, express each such integer in hexadecimal. like 5FB or A71. Now, assign one of sixteen notes to each of hexadecimal digits. Play them in sequence. Bam! (Use recordings of piano notes or guitar chords for all I care, or bells.)
Plan B was to just pump the raw text of the notification into minimodem (“general-purpose software audio FSK modem”), set to a verrrry low bitrate. I figured that after I heard the same few common sequences multiple times, my ear would get trained to differentiate “missed call” from “new email”. Then I’d be able to plausibly argue that I could hear modulated digital data. 🕶️
I had heard something like this on a podcast from an accessibility expert. They had morse code ringtones, so they could know who had called without looking at their phone.