Backstory: I was listening to a podcast today, "Startups for the Rest of Us, episode 412", and the hosts mentioned there was no software solution to track customer feedback. Sure enough, I google quickly and there were some that could fit but nothing small and simple like https://headwayapp.co/ for product release notes.
The Idea: A simple customer feedback tracker.
Deep Dive: You would keep this app simple and track feedback on potential features. At first you could limit it to one user and as you gain traction, implement role/user based actions.
Validation: Nothing like this exists and it was mentioned as a need from a SaaS founder.
Monetization: You would charge a monthly subscription. Keeping the app small would allow you to charge a small fee to attract a lot of startups and small companies. Eventually you could add tiers with additional features.