Well that is what I mean by research - perhaps simply giving people more money will make them happier than giving incentives for specific stuff. But the original idea for the company is to benefit indirectly from the payments (fitter, happier employees), so I assumed the additional payments should be justified like that. Of course it could also lead to resentment: "if you can afford to pay me x$ for gym and holidays, why can't you afford to pay me a higher salary". Who knows?

Actually happiness research seems to indicate that spending money on experiences rather than stuff (for example) is a good idea. But I am not sure if it follows that it still works if you make people spend on experiences instead of stuff.