The whole installation is connected via a Netduino board to Twitter and monitors a certain (configurable) hashtag. Tweets found are then displayed on the split-flap display. Heart of the installation is a MCP23018. The split-flaps themselves were recovered from an old train station.
The current installation is only a proof of concept (limited to 8 characters) running in demo mode (showing a set of pre-configured words) and is not optimized yet (characters turn one-by-one, not simultaneously).