This is a deceptively difficult question: Simple is used by thousands of healthcare workers and health systems managers.
Staff at hospitals and clinics
Healthcare workers are the main users of the Simple Android app. They register patients into the hypertension/diabetes control program and then monitor each patient's health over time. But there are key differences.
Medical officers (MO) are empowered to treat patients, which in the context of hypertension and diabetes care means that they can titrate (i.e. intensify) a patient's medications if appropriate. In a small hospital (PHC), medical officers might be the primary users of Simple. In a larger hospital (CHC, SDH, DH), many medical officers are too busy to enter data and more junior staff will manage Simple.
Staff nurses, junior staff nurses, etc
In many facilities, nurses manage the use of Simple. Particularly in large facilities, a Non-Communicable Diseases (NCD) Corner is likely staffed by nurses who take BPs and manages Simple. Patients with high BP measures should be referred to a medical officer, who will manage treatment. Often patients return to the nurse after seeing the medical officer, so their data can be entered. They are the primary users of the Simple Android App.
Community health officers
Community health officers (CHO) are mid-level health staff who can treat some non-complex conditions and are primarily the senior staff at Health & Wellness Centers (HWC) in India. In some contexts, the CHOs treat patients and record their details in Simple. Note: There are many HWCs in India, so there are many CHOs.
Data entry officer
Some hospitals have dedicated staff for data entry. They are responsible for submitting monthly data (usually in spreadsheets or paper forms) to local government officials. They might correlate data from the paper registers with records in Simple and they might compile totals from the Simple's Progress Tab to submit as part of their process.
Chief medical officer
The chief medical officer manages the hospital and is usually the most senior doctor. The chief medical officer might use the Progress Tab in the Simple Android app to monitor the facility's progress towards controlling patients' blood pressures.
Health system managers represent a wide group of people who are responsible for optimizing the health system to help more patients to control their blood pressure and reduce deaths.
State or national officials
At the Ministry of Health in a state or country, officials are responsible for tracking many programs, including hypertension and diabetes. They might use the Simple Dashboard to track progress in their region, but more likely they see charts when a nodal officer or cardiovascular health officer visits with them once-per-month to advise on how to strengthen the program.
State of district nodal officers
A nodal officer is a government official with a particular focus area — there are NCD nodal officers in many Indian states or districts. In some states (e.g. West Bengal), the district nodal officer has a similar function to the cardiovascular health officer. The nodal officer might monitor the Simple Dashboard or (like the state officials) they might only see the data when a cardiovascular health officer shows them charts.
Cardiovascular health officers
CVHOs are surveillance officers hired specifically to manage 1-2 districts of a hypertension program. The India Hypertension Control Initiative has many CVHOs across India, primarily focused on improving the program. The same people are called different things in other countries. They are the primaryusers of the Simple Dashboard.