There is a remedy you can buy over the counter. I'm not sure of the name, it varies from country to country. Basically you put it on your nails and it is a vile tasting stuff. So once you bite your nails, boom you get this taste, and hopefully think twice about biting them again.
Its basically clear nail polish. I've had this same habit for years. I however dont care. Keeps my nails from getting longer then 75% the size of my finger.
I wholeheartedly endorse Dstates' recommendation. To think the amount of time and money I put into manicures and pedicures, and there you are nibbling at those toe and finger nails.
Where do you live? I'll tazer you myself...