J.D.
Hi- we too are battling this! I just looked into the "No Bite" polish- it's sold in the nail section at Wal-Mart. I was going to buy it, but if you read the fineprint, it's **NOT** non-toxic! It has a warning about ingesting the stuff. Well, duh- what about the kids that just don't care and keep biting? So, I brainstormed and came up with many of the ideas mentioned here. I will say that I agree with a previous poster about anxiety possibly being related to nail biting, but also I agree with the poster about boredom. I pick at my cuticles and tend to do it when I'm watching TV.
Good luck!
J.