A superheat controller is exactly what I'm building, but I'm adding more user-friendly HMI and some additional features to control condenser/evaporator throughput and so forth too.
I'm pretty familiar with Danfoss, Sporlan and Emerson controllers; probably cheaper to use one of the less expensive options that what I'll end up building but the point is the exercise of building and programming 
What I'm actually building is a portable half horsepower water source chiller that has tight control of the process stream and minimizes water usage on the condenser side via flow control to optimize the condensing temperature. I knew I'd likely need to build from the ground up, but I've been surprised with Arduino shield offerings so far.