Gleb Polyakov and Igor Zamlinsky of Atlanta, GA have designed this proportional-integral-derivative (PID) controlled espresso machine. Based upon their observations after reverse engineering a number of espresso units, the pair worked on developing a machine which would be reasonably priced, open source, be espresso pod compatible and have a PID controller. Temperature and pressure are controlled by an Arduino.
The resulting machine is expected to retail for $400, and the project has been fully funded on Kickstarter.
Here’s a link to their video demonstrating this project.