Ive done some basic research on this topic and so far Steamist has come out in front for integration, from what I've read anyway. From my recollection the device communicates over rs232, but looking back i can't find any reference to it and it would make more sense over wifi, could be thinking of MR Steam!?! I currently believe you have On/Off control & MEM1&2 when using the Houselogix driver.
Steamist Control4 Compatible Controller - https://www.amazon.ca/gp/product/B007L4LSAE/ref=ox_sc_sfl_title_4?ie=UTF8&psc=1&smid=A3DWYIK6Y9EEQB
This is from Steamists FAQ's, -http://steamist.com/resources/faq/
"Is a Steamist Steam Shower System compatible with Home Automation Systems?
The mySteamist app which is standard with the 550 Digital Control and optional with the 450 Digital Control allows for integration with two of the “professional” (not DIY) home automation systems, Crestron and Control4.
Crestron has published the application for integrators to use that will feature Memory 1, Memory 2, Off and System Status display. Click here for more information on how Steamist connects to Crestron.
Control4 integration with similar features is now available through “TheDriversLab” Steamist Driver and App. Click here for more information on how Steamist connects to Control4."