Wow, like Edison said, invention is 10% inspiration and 90% perspiration.
Some areas I found intriguing:
1) Biosensors based on analyte-specific electrodes/membranes. That combines solid-phase chemistry and electronics. It is an immense field and is continuing to grow.
2) Sensors based on energy transfer reactions, e.g, fluorescence. That area is mostly chemistry.
3) Laboratory and diagnostic modeling. That is mostly computer and statistics.
Since this is an electronics forum, I would recommend you look into the first option. As for a specific project, there are many. Pick an organ system or disease that interests you. Then look at current diagnostic methods, and go from there.
For example, let's say you were interested in heart disease. I pick that because it is also an immense area and has significant morbidity and mortality associated with it. Then look at current diagnostic methods, e.g., EKG, serum enzymes, troponins, etc. You will find new tests based on changes that happen to serum proteins as a result of ischemia (lack of adequate tissue oxygenation, e.g., heart muscle), such as changes to albumin that affect its ability to bind certain elements (cobalt, for example). Then, you might propose working on a probe to detect the same type of changes.
That is just one example. The first step is to pick a disease that is important in your population. Then pick a good faculty advisor interested in the same area of research.
I was just looking at an oscope for PCs, maybe a super low cost heart monitor adaptor for a PC? It uses the audio in functions on a PC. My thought is low cost technology, if it works, could be a godsend to remote locations that have very little in the way of technology.
If you are looking for something that is fairly straightforward you may want to consider designing your own version of a heart-rate monitor using an LED. Here is a paper on one version of the design I am suggesting.
we had a project for school were we had to make a medical device.
we made a spirometer. (a device you have to blow in and we register which way you blow and how hard, the results are put in a graph, graph is diff. for smokers and healthy people and people with problems @ their lungs incl caughing).
the basic setup:
a ultrasoon speaker, a ultrasoon mic, a microcontroller (used 1 of microchips ds series) that takes alot of samples . samples can be stored on external memory or send to the pc after a couple of tests.