UP Digital Bureau and Unteleported tech agency present the Tweephone, an analog Twitter client. In the world of short messaging this is about as retro as you can get. Remove the phone from the switchhook, use the rotary dial to enter your message (with the appropriate number of dial rotations to get the letter you desire, similar to a cellphone keypad). You message appears on the LCD screen, and to send just hang up the phone. The messages appear on the Tweephone’s Twitter account.
You can find the Arduino sketch on the project’s Github page.