Referral prizes are standard practice in gyms and health clubs. But, you can ramp it up a notch by using contests to get testimonials, brand recognition, fitness challenges as well as referral bonuses. It is also a great way to collaborate with fellow businesses who share customers with you, sharing the cost, co-op advertising. It works great with social media. Check out this article by Wendy Keller for more ideas and a checklist of how to do a contest.