Meet Starling: a modular, open source display with WiFi that lets you share custom messages with the world. You can change fonts, scrolling settings, and other settings. Starling supports IFTTT and REST APIs. Its mobile friendly web app lets you customize how Starling behaves.
Starling measures 70 x 20 x 60mm. You can chain LED matrices together to form larger displays. More information about various Starling models is available here.