My side project StatusGator, which monitors service status pages, has been running profitably for the last year. It took about 3 months to become profitable and it's only so because my time is "free". (But isn't that always the case?)
I don't do anything to promote it so growth has been entirely organic. I get a few free sign ups every day. Although they very infrequently convert to paid, I keep expenses low so it doesn't take many paid users to be profitable. If I had more knowledge of how to market such a thing, I believe it could be a reliable revenue source. But I'm otherwise happy that its relative profitability motivates me to maintain it, as I find it supremely useful for my own personal use.
I don't know if statuspage.io is similar to what you're doing, but their blog documents much of how they got profitable. Makes for interesting reading.
A little different: Services like statuspage.io, Runstatus, Cachet, Status.io, etc. all offer status pages. StatusGator aggregates all the status pages you care about into one status page for your own reference and also sends you alerts to email, Slack, etc, when those pages change.
I love the idea of blogging about growth and profitability. Seems like that could be a good marketing channel, in addition to being very educational.
You can find out a lot of information about your customers by calling them. How did they find SG? Why do they need a meta status page? How much value does does SG provide over using disparate status pages? Why did they stop using SG after several days?
Once you've talked to all your customers you should have a lot more info you can use to market to new customers.
I don't do anything to promote it so growth has been entirely organic. I get a few free sign ups every day. Although they very infrequently convert to paid, I keep expenses low so it doesn't take many paid users to be profitable. If I had more knowledge of how to market such a thing, I believe it could be a reliable revenue source. But I'm otherwise happy that its relative profitability motivates me to maintain it, as I find it supremely useful for my own personal use.