That's one awesome regex debugger! Going after such a small niche is a great idea as long as you know that the market is big enough to provide good ROI in both

That's one awesome regex debugger! Going after such a small niche is a great idea as long as you know that the market is big enough to provide good ROI in both percentage and nominal terms. I don't think the worry from a competitor "adding a feature and crushing you" is a very likely threat. As long as you can stick it out for a few years to build a brand name and continue to keep in front of the indefinite stream of people learning regex you should be fine.