BRCK is a wi-fi router and mobile modem in one, with eight hours of battery life to keep it going when the power runs out. It can sit in an office connected by ethernet and switch seamlessly to a 3G or 4G connection if the line goes down. It can also support up to 20 wireless connections and has 16 gigabytes of storage so it can work as a back-up network drive. Connect it to some processing power, such as a Raspberry Pi cheap computer, and you have yourself a mini-server.
You can learn more: http://www.kickstarter.com/projects/1776324009/brck-your-backup-generator-for-the-internet