Although twitter is considered a simple push-messaging service, by combing an Ethernet-enabled Arduino board and some crafty coding you can control an Arduino board via twitter, and also display data from twitter - and have the Arduino 'tweet' back a reply with various data. This can be useful for remote control of ... almost anything, and remote retrieval of data that can be captured by an Arduino system.
Thanks to 'xenonjohn' all this has been explained and documented well, so click here to read the instructions. And we're on twitter, so follow us for news and product updates as well.
To build your own twittering Arduino system, use the Freetronics EtherTen. Apart from being fully Arduino Uno-compatible, it has onboard Ethernet, microSD socket and supports optional Power-over-Ethernet: