Having tweaked the larger control application to death, I purchased a couple boards to start working up an I2C control system suitable for an all in one touch screen platform. For less than $50 I acquired an USB to I2C board, 16 Digital IO board and a 8 channel 12 bit analog input board to relieve my boredom. A bit of experimentation and a test application have sorted out power, 5V reference,communication and timing issues. Response is good with analog channel scan steps of 80 ms X 8 channels, and scan interleaving for digital commands. The goal is to use 0-5V sensors for temperature and pressure, and have enough digital outputs to operate the ball valve actuators. Found some 0-5V output analog sensors AD22100K with -50 to 150 C range that should be a good fit, still looking for low cost wet pressure sensors, ones that I have found are a bit spendy at $110 each but they are wet sensors with threads for pipe installation and a 5V output. Still have not picked up a PWM board, but one with 16 channels can be had for around $14, and coding is not hard to implement.
Here are a couple pictures https://picasaweb.google.com/kevin.ladue/I2CBoards
Here are a couple pictures https://picasaweb.google.com/kevin.ladue/I2CBoards