Say I have an idea for a webapp product that I believe would be a no-brainer for a specific group of companies to offer. Then say I decide to build that product for fun, and have a fully working webapp, ready to go. What’s my next step?

To make up a silly example, that is not what I have in mind: A fridge door open counter app. Any time you open the fridge door, you scan a QR code that you attach to the fridge. This is clearly something that wouldn't be of interest for real, but let's just pretend that for a significant portion of people, this would be awesome. Let's also pretend that if this idea were presented to the board(?) of any one of the major international fridge makers, they recognize that, and predict that the edge it would give them over their competitors would be advantageous. It's the sort of thing that they will be able to promote as a free benefit when you buy their fridge. There would be minimal costs to the company to integrate with the system – they don't actually need to do anything if they don't want to, they could just make the system free for anyone to use and promote it to their customers. They may wish to integrate more tightly and have something in their app/receipts/online account/etc. that logs you in to my system.

Of course it's also the sort of thing that they could develop in-house if they wanted to.

However, what I have to offer is a fully working system, ready to go almost immediately (I imagine they would want to brand it, but that's all that would be needed). I will note that it's only me and a couple of friends that have used this so far, so there's no userbase that I would be handing to them. I recognize that this also has testing implications, but I figure some sort of deal can be made whereby it's free/low cost until they hit a certain number of users.

What do I do next? Do I contact one of the fridge manufacturers directly? All of them at the same time? Who do I ask to speak to?

In case you hadn't guessed, I'm a web developer with no business/marketing experience. I did have an idea for a project (non fridge related) a while ago, which I made for myself and has been awesome. There are some national/international companies who I believe would jump at adding this project as a benefit if I got it to the right ears.

I also have no idea where to start on how to present this in terms of business. I'm open to all options – from sell them the entire thing to manage it myself and charge them to use it (which could be exclusive use, non-exclusive use, or something in between), but I don't know how to approach that part.

I do, however, know how to go into a room of people and present a product well, so if I can find the right person/people to talk to, I am confident that I can convince them that this would be beneficial to their company/service.

Thanks!