You can find those challenges yourself by volunteering your time at the grass roots level. One of the top of my head - One of the challenges in mass immunizatio

You can find those challenges yourself by volunteering your time at the grass roots level. One of the top of my head - One of the challenges in mass immunization (especially in poorer countries) is that the 'last mile' data is very sketchy and mostly self-reported. Many times people just have to assume that immunization campaigns are successful without proof. It would be nice to create a device/method/protocol that could automatically collect data, like say who was immunized, what were they given, number of doses, etc, etc. Conceptually the challenge looks to be easy, but in practice at the ground level is where the real challenges lie. Another idea is creating a smartphone app that end-users can upload test results via the camera. for e.g. in the case of tuberculosis, once you administer the test, you have to observe a color change on your skin within a certain period of time. The key thing here is that in places where the number of doctors are few, we want to create a system where the patient who is taking the TB test only goes to the doctor if they actually have TB. A smartphone app that can deal with various lighting conditions, various resolutions, various color casts (due to auto white balance issues), etc, etc would be an interesting option.