Looking at this function in the NSA:
probe. addCallback( sCallbackFunctionName, sCallbackArguments [, iSecLevel] )
I usually leave out the last argument--iSecLevel--and am thinking about trying to use it, particularly where the callback triggers an action rather than just getting a response. Anyone know what the valid values for iSecLevel might be (other than read = 0) and how they translate to users/ACLs?