Troll Bait let you display text on my badge from a public website.
It serves a simple website from a Raspberry Pi that accepts text input from a user. That text input is passed through a sentiment analysis API before being transmitted via UART to the badge where it is paginated (er .. line-inated) for display on my badge. If you are a happy hacker, then your text shows up unadulterated but if the sentiment API determines your text to be "negative", then your text is displayed on the badge with a red background and the caption "* * TROLL! * *". Towards the end of the weekend I also opened up a web API for the device and a few souls happily hacked it for the following hours while I wandered around with god-knows-what displayed on my chest.