With a properly implemented water/methanol injection system, you should be able to arrive at maximuum power AFR and MBT without ever experiencing knock.
I tune without water injection to the threshhold of knock and then pull back a bit to find my base tune that I revert to in the case of a WI system fault.
Generally I only monitor for knock during tuning - I use this:
http://home.netcom.com/~bsundahl/kno...nockSounds.htm
And the DIY knock cans:
http://home.netcom.com/~bsundahl/kno...ten/listen.htm
I attach this to my tuning computer while tuning.
Of course I am relying on my ECU's knock sensing / timing retard response if I cross the edge somehow.