The first thing you need to ask yourself is why you do not have good knowledge of the industry and how do you get this? Once you have learned about the industry you will find that there are hundreds of glucose meters and heart rate monitor companies. What would make your device different? The next question to ask is what is a niche area that you can dominate? What sensors are currently available for wearables and what is a new way to apply them to generate value? Most importantly you need to ask yourself what problem you want to solve and why. Use the Feynman method: Find the problem first, think really hard, and then come up with a solution.