No, there is no other built in feature for auditing use of Site Admin.
I have opened change requests with HP for that very feature, but they have yet to address them. If you need that functionality too, open a change request with HP. Part of their prioritization process is based on how many clients are asking for the change. The more who ask, the sooner it will get done.
Because of this lack of auditing, I have resorted to creating my own interfaces to the SA API, and creating my own log files for those interfaces. Behind the interfaces I use one master Site Admin account to execute actions, while tracking the user using my interface through my interface's log files.