Nobody wants to flick on a light in their kitchen to see a bunch of cockroaches scurrying about. And depending on where you live, its not like a rinky-dink little roach motel will get the job done. Those suckers can be huge. Sure you could use a baseball bat or a gun, but if you don't get the jump on them one of these super-roaches could take it right out of your hands. Then it would have a weapon. That's why you have to get serious with an electric roach motel to fry the little buggers.
The device shown here can generate 10 pulses at 400 volts per second using a 9 volt battery and a PIC12F683 with a switchable clock speed. I'm not sure what is attracting these roaches exactly, but you can be sure that if they ever cross over the plate, they are as good as dead. Hit the link for info on how to make your own. [Project Page via Hack a Day]