The default keyword is PROG unless the user has changed it, and the PIN is the same as the alarm PIN. Not sure why the keyword is necessary given that the PIN provides the security though, but it is.
Hi guys, I have the HSA6500 that also has this feature. The SMS commands work on mine.
FYI, my disarm command looks like "PROG 1234 MODE∶D", where PROG is my keyword, and 1234 is my PIN.