exceltrading

I had spent years building a reputation in various forums, chat rooms, etc. I had released some free software that a bunch of people used. So it wasn't hard to get users when I released a paid product.

I'm not sure this side project could be achieved any other way.

There definitely is for excel. Both for consumer add-ins and internal business add-ins. I've thought about it, and even started on the idea a few times, but have given up. There are just so many components of the system that are outside of your control as a developer. Someone with the appropriate resources might be able to do something neat.

I was quite lucky. It will help fund an early retirement.

Yes, about half my code and effort is handling stuff that an "app store" usually would.

Ha. And given how much of the world runs from excel sheets, I'm very surprised it's not a more popular business model.

I sell an excel add-in that integrates with some popular trading software. It makes life easier for traders. It has a couple thousand users paying around $10 a month. That's about as specific as I want to get.

It required a little domain specific knowledge to create, and a recognized name among trading forums to initially market. Otherwise it's super simple and I'm continually surprised that there are no real competitors.