when i used to walk an hour to work (and another back), i considered using morse as an interface to a portable computer (for editing and playback of text). it's easy to hear and understand, even when there's considerable ambient noise, and data entry would only require a single button (plus perhaps a rocker switch or similar to scan through existing data).
at the time i had no real idea how to implement it. now i think i could do something with an arduino or similar. but thankfully i now work from home...
I've also thought about a pocket-sized clicker device that you could use to send Morse to your friends, perhaps interfaced with your phone. Or maybe, as you said, you could use it as an input device. One day when I have some extra time on my hands I'm sure I'll sketch one out. But I've got to learn Morse first! ;)
at the time i had no real idea how to implement it. now i think i could do something with an arduino or similar. but thankfully i now work from home...