I too am looking for ways to keep my girls entertained as winter approaches and they are spending more time confined to the run, which is now standing on paving slabs and bark and they don't have grass to scratch around in anymore.
I tried a CD, they paid no attention to it whatsoever. I tried hanging broccoli. It didn't keep them amused for long, the heads had gone with in a couple of hours and then they got the stem off the string and finished that off in not very long! I am thinking about getting one of those peck block things, but don't know if it's worth the money, I guess the only way to find out how long it'll last my four, is to buy one and see! I saw one website selling chicken boredom buster packs that contains cuttlefish bone. I'd never of thought of giving that to chickens, I'd have thought it would contain too much salt unless pet shops remove the salt before they sell them. We are also in the process of covering part of the run so that we can make them a bigger dust bath.