I did a bunch of research on keyword volume for the problem space, looking at existing alternatives, and seeing where I could differentiate.
I decided to build completely in public, posting updates on Twitter every week. This is the day I made the first post and you can find the full thread here:
In the weeks following I got basic stuff working like authentication and interfacing with the Twitter API.
Later I ended up skipping some weeks but having this thread really helped me come back to it and re-focus again. Building in public is a good motivator.