I think it is interesting technology when you look at prospects of closed loop peak cyl pressure angle control, but I think that is still a long way off the aftermarket world. As for ion current knock control, it is not very useful in anything but OEM applications, there are just too many combustion irregularities to allow it to be implemented in a DIY scenario. On the moderm BMW's with it for instance even a small change to the fuel mixture completely upsets it.
