I built out a fully custom pool automation controller using a Particle Photon and a custom PCB printed by OSHPark. The Photon has some integrated web functionality and supports HTTP POST and GET, so this seemed like a great way to learn how to make a SmartThings Device Type. After tons of trial and error (wow is the SmartThings stuff finicky to write code for), I have two fully working device types, one to control my Pool Pump, another to control my Solar heater.
The biggest improvement I made was to leverage the Particle Photon for much more custom use than what was previously available (mostly turning on and off switches).
More information and how you could make your own or customize my Device Types to suit your needs are available on the GitHub repository: https://github.com/Here-Be-Dragons/Pool-Controller
Here is the actual controller:
And for a bonus, I also have it all logging and graphing to a Graphana dashboard: