Vanilla is a product of Lussumo:
Documentation and Support.
Oh dear fucking Cthulhu, this is like something out of a John Brunner novel: NewsTweak.
TL;DR version: it's a plug computer like SheevaPlug or PogoPlug ... or the rather less benign PlugBot. It runs Linux and has wifi and a bunch of preconfigured software to do interesting things on whatever wifi network it finds itself on. You'll notice it has an extra mains socket on the front, so that it looks like a rather clunky surge suppressor or similar adapter.
In the case of NewsTweak, it uses ARP spoofing to change the text displayed on certain web sites. In the demo video (see that link at the top?) we see NewsTweak changing a headline on the BBC News website.