I have a most excellent idea for a smart phone app.
I have years of market research and the platform to sell it. Of course, there's always the chance it would flop - but I doubt it. It is a niche market and most likely will need careful pricing/monetization.
Do you have the skills to make it? It doesn't need any flashing lights or moving parts. It does need to collect, sort, and display data. It also needs a lot of if -> then display things and a simple user interface.