I built Food Photo pro bono for an intermittent fasting study. The idea was simple: let participants take photos of their meals on their phones, and give the researchers a way to review them.
It's a small React app. Take a photo, add an optional caption, mark it as before or after a meal, and submit. The images go to S3. A scheduled job sends text reminders, and a separate report page lets researchers browse the photos.
The backend uses AWS Lambda and the Serverless Framework. I also tried serving the report page directly from a Lambda function. It worked, though I wouldn't make it my first choice for serving a website.