If you run MongoDB on server (example AWS or DigitalOcean) you can easily connect to it with MongoDB connection string.
It's advised to run on separate server as MongoDB takes up a considerable amount of RAM and it's never a good idea to run your database service on the same server instance as your production services. I run mine on AWS lightsail for $3,5/month for now.
Will look into adding on-premise, if this gets any traction.
As developers can use Robo3T and write queries, the ideal customer in my mind is a smaller team/startup where developers setup metrics for marketing/product team as they need them but can't use MongoDB.
I'm not sure how to market this as developers need to do the setup, but product or marketing actually needs it.
Any advice on how to market?
You might want to consider adding an on-premise plan? I think most DBs are not publicly exposed on the internet?