I have a Premise driver for the IntelliTouch system that does some basic things using the A5 version protocol. It is in the Premise Downloads area of Cocoontech. It does do the 0x88 Set Heat message (the high bit seems to imply a Remote address is doing a Set versus a Response packet - I.e., current Heat settings is 0x08). I use a Digi One SP to convert from RS485 to IP. I ended up setting the termination dip switch on the serial converter, as the IntelliTouch Controller seemed to be having difficulties sending data otherwise (yes, I did connect the ground wire).
One frustrating thing (besides the fact that Pentair doesn't just release the silly protocol) is that I have not yet determined a way of querying the current heating set points. No 0x08 packet is generated unless a 0x88 packet is first sent. So you can't see the heating set points until a Remote device (which could be the driver) sets them. Not a problem after the data has been acquired, but still annoying.
Regarding the byte following the A5 in the header, I have seen 0x00, 0x01, and 0x02. I just use 0x01 and it seems to work.
My IntelliChem/IntelliChlor is separate, and I have not looked yet at that bus. Maybe someone has some information?