How hard might it be to catch a bully in the act with a hidden mike or a friend with a cellphone or some such? That sort of thing was completely impractical in my day -- I'm not sure what tools kids have now.
I suppose it's worth trying, although the victim may not be so keen on having his or her own victimization recorded for posterity.
I have also heard that among girls, one common form of bullying these days is to pretend to be the victim's friend long enough to get some embarrassing confidential information, and then spread that information around. Modern technology makes that kind of sting a lot easier.