Another device from long ago...the Microwriter Agenda. This was a pocket sized PDA employing a chorded keyboard for text entry. The ideas behind these keyboards are that multiple keys are pressed to produce single letters and that the keys to be pressed represent the shapes of the letters concerned (to some extent) to aid memory.
If you read the advertising pack link here for the Microwriter Agenda, you'll wish that you had one, and then you'll also wish that an updated version was available for the iPhone!