Building Ed Konowal's Raspberry Pi-based Internet Pressure Gauge (as seen at SIGGRAPH 2014!) costs about $425 in parts ($100 for the vintage gauge on Ebay, including metal-shop time for the refurb), or you can support the kickstarter for his kit, which gets you everything except the gauge for $310 (for $500 he'll build you one, but you still have to supply the gauge).
Internet usage is typically measured in Mb/s (Megabits per second) and dispalyed as a graph on a monitor or smartphone. In this project I've taken the same data and translated it to a real world gauge. A steam pressure gauge from the early 20th century.
Data is collected by polling an Internet router, in this case the router for the Vancouver Convention Center. The data is converted to a 0-200 scale to match the steps on the pressure gauge. Next the data is sent to a microcontroller which moves a servo to the appropriate postion. The servo is connected to the needle of the pressure gauge.
While this seems relatively straight forward, it required a lot of trial and error and adjustments to get accurate physical movement that matched the Internet usage data.
The most interesting thing in this entire project was the realization that Interenet usage statistics are usually averaged over a longer period of time. The Internet Steam Gauge checks utilizaiton every 10 seconds and is therefore more accurate than most monitoring systems.
(via Beyond the Beyond)