The only way to keep your cat from hunting and killing other animals is to keep them inside. The question How can I prevent my cat from killing animals and birds? shows that putting a bell on the cat is not 100% effective.
The cat will still hunt, the bell may or may not give the other animals sufficient notice to escape.
We have the existing question Laser pointer: does a no-win situation risk psychological harm to cats? with a GREAT answer by Zaralynda. that speaks to psychologically issues. But keep in mind, bells don't make hunting a no-win situation, it just makes it harder for the cat to catch the animal.
