How do keep rabbits off lawn without fence?

There is now a suspicion that one of the reasons my lawn has brown/yellow/dead patches on it is because of the numerous rabbits visiting the lawn and eating and urinating and leaving droppings. Any suggestions as to a commercial product (or home remedy) I can use to repel rabbits? I would like to avoid the hassle and unsightliness of fencing or mesh or any physical structure/barrier.