I don't feel like it's terribly hard to predict that the Mac gaming market is going too small to make financial sense for a solo-dev game
Users follow other users, if they can.
I've been thinking about doing something like this recently but I'm not a heavy mac user these days. Any tips on what people are looking for in small tools?
Ask yourself, what tools can I build that are not only useful to me, but maybe useful to others, and start there.