When looking at the attempt to optimize health, there are three main concern groups that have come to mind as I contemplated these concepts over the past decade. I'll explain these three groups individually. The overview of the three groups are (1) people with autoimmune diseases (or taking immunosuppressents), (2) people with blood cancers, or (3) people who are pregnant.
Autoimmune diseases can be overgeneralized as a disease where a portion of the immune system is doing too much, typically attacking a part of the person's own body. In this conceptual scenario, part of the body is doing more than 100% of what it should be doing. Common treatments for autoimmune diseases work by immunosuppression, meaning the treatment tries to reduce the immune system's effectiveness. In this scenario, we would not want to increase the immune system's effectiveness as it could have adverse effects. We wouldn't want a game that would do the opposite of what the medical community is trying to do for these people. People recovering from a bone marrow transplant or other organ transplant may also be on immunosuppressants and in these subgroups we would not want to increase immune effectiveness.
In people with blood cancers, the cancerous cells are already refusing to accept they are not the bad guys. if we strengthen the healthy cells, we would potentially strengthen the malignant cells. In blood cancers specific to white blood cells, this could be devastating, as the immune system functions primarily through white blood cells.
In the third category, a person who is pregnant has cells tha are not 100% native to the mother's body. The fetus developing contains genetic material that are part from the father. The immune system is carefully tuned to accept the fetus and nurture it. Trying to optimize the immune system that could be considered naturally suppressed, while unlikely to believe it could cause a miscarriage, could upset the balance required for healthy development of the fetus, which could have unknown effects on the baby when born.
There are likely more subpopulations beyond these three mentioned above. I believe this strongly suggests the necessity that any game that is designed to have an effect on optimizing physical health or immune function should be restricted or require a prescription.
With available technology, we could believe that the physical device should not be part of the prescription. If the method requires both prescribed physical hardware in addition to the actual application software (mobile app) itself, this could fall under old drug laws and therefore both be unnecessarily expensive and disallow therapists from prescribing games. Recommended hardware requirements for a device do not actual require the delivery of the hardware with the software application, which could allow it to be a new category of treatment.
Devices that would be able to load the mobile apps and video games would need to be those that can accommodate independent developers. It would be unreasonable to only allow the hardware manufacturer to publish these applications.