List all lot of types of android apps the main groupings and ones you find of interest. Each day research the gripes people have with each of these types of apps. Take the extra time with your app to serve well desktop mode, Tablet mode and phone mode with extra options for each where required or better served.
So you should after such work have a better idea of where you want to tackle in the market.
Here you could do a really good job and no one notices you more so than gaming.
So lets think about general and smaller tasks this app is going to do. Swiss army knives are good but not always bought.
So ask your self what is going to be it's general task and how many people might like such a task or service.
If your stuck still after all such work to hit the market then maybe you should try gaming or if your still wanting to be more inventive you could try education in engineering there will always be something you can prop up engineering wise as a demonstration app that could catch the eye of programmer recruitment.