I think my question would be have you looked back into the strategy of physical rewards for health motivation? Rather than recommend services offering gym discounts, health supplement discounts etc. I'd rather go back into the reasons why you want to offer rewards in the first place.

From most industry best practice and studies into motivation, if you make the process transactional (do good thing, get spa discount), you'll actually lower motivation in the long run and damage any possibility of turning the healthy activity into a habit.

Example 1: Studies where patients were paid money for adherence have repeatedly shown poor results, as patients begin to cheat the system and created something transactional.

Example 2: CrossFit started from day 1 with an idea of standardised measurement (i.e. quantified self) and competitive leaderboards (i.e. feedback loops). Even though there are no mechanisms to stop an athlete from lying about their own time, the organisation has created an entire culture and international business off of the idea of people competing with themselves and baselining against strangers around the world. Standardisation, feedback loops, and gradual difficulty progression are all key ingredients to how CrossFit achieve this.

Instead, I'd focus on how your rewards program can be intrinsically rewarding.

I wont say "gamification" for the sake of dropping a b-word but if you pick up a book called 'Drive' you'll get a good primer into the underlying psychology of how/why game/reward systems can improve a positive behaviour.

I've passively been around the health tech industry for the last few years so happy to follow up on a call, I also have a few contacts who might be helpful.