The next example for on-device calculation is a risk calculator. John contributes background status and activity with no-peek, and then alerts and risk scores are delivered to John also using no-peek methods. The calculator can have inputs including John’s age, comorbidities, test results, data from phone sensors, as well as external data such as mobility, the caseload in the region, and so on. Further, the calculator can also be told the activity John expects to do: Is it very vigorous, like going to a gym and for how long, and is the gym crowded? Is it indoors or outdoors? And is John going to spend time with other people who are vaccinated? By taking this input, the risk calculator uses machine learning to calculate John’s risk.