This could also be an early precursor to Twitter!

Folks have certainly mentioned other incarnations:
- annotations in books (person to self),
- postcards (person to person),
- the telegraph (person to person and possibly to others by personal communication or newspaper distribution)

but this is the first version of short note user interface for both creation, storage, and distribution by means of
electrical transmission (via telephone) with a bigger network (still person to person, but with potential for easy/cheap distribution to more than a single person)