You can process personal data collected via a health app for secondary purposes if the processing is compatible with the purposes you originally collected the data for. Any big data analytics for market research, communication, health insurance etc. is subject to data protection rules.
Advertising
Clearly ASK your user for authorization to use advertisements. This authorization must be asked BEFORE the app is installed.
Ask for an explicit consent (OPT-IN) if you will use context-specific advertisement in the app, sharing the personal data with a third party or by processing the data concerning health. If not sharing personal data nor processing is the case, you must give the user an OPT-OUT on the advertisements.
Research
Processing data for scientific or historical research purposes needs to be done according to any national or European legislation regarding secondary processing. This implies:
- Minimization of data collection (only what you really need).
- Anonymization wherever possible, if not pseudonymisation.
Please be aware that for scientific, statistical or historical research purposes clinical trials and deontological rules may apply requiring involvement of ethical committees, etc.