I bought this ball for Angel when he first came to me. I recorded something mooshy and embarassing.

and stuck it in his cage. At night I would hear him give it a "shove"---that is all it took to make my voice come on "It is ok Angel---Mommys here!" I swear he knew it would comfort him and he did it quite often at night (and probably during the day when I was at work).
It is meant for dogs and is called the "Talk to Me Treat Ball"....I never put treats in it---just recorded my voice to sooth my birds.
http://www.aspenpet.com/productDetail.cfm?id=2329
I have seen them at Petsmart and you can buy them at
www.qvc.com.