Love this idea. I think it could be especially effective with companies that offer consulting work. In addition to spreading through the company, it could be viewed as adding additional value to the service being provided.
This is a great idea. I feel like this could have added benefits if the health leave days of various employees were shared in order to be involved with a team or group fundraising effort. Being involved as a group in an athletic activity has the potential to increase group cohesion. Having the multiple benefits of promoting employee health and increasing team productivity.