Onion Omega (https://onion.io/)
Dimensions: 28mm x 42mm
OS: OpenWRT Linux
Processor: 400MHz
RAM: 64MB DDR2
Flash: 16MB
Wireless: 802.11 b/g/n
Ports: 18 GPIO
Language: Python, Node.JS, PHP, Ruby, Lua and more...
(http://t1.gstatic.com/images?q=tbn:ANd9GcQKkcYTkeqqII_Dug7NVe5AMsQBx5r3SFJYU-dcaQKN4noG0lBt)