This is one of several that I've tried, and I'm still looking for the best one for me. I think if you don't subscribe then they limit the number of cameras you can add, and apparently they also have a time limit.

Ubiquiti has a pretty easy to use camera and wifi design tool, but of course it is limited to their hardware.

Axis has one, but it's mostly limited to their cameras and I didn't like it too much.

Backstreet Surveillance has one that's alright but also limited to their cameas.

System Surveyor is pretty good and has a free tier. It is pretty good and does way more than just cameras, but I still find it limiting in several ways.

I've tried a few others too, but I haven't found one that has all the features I want while still being easy to use. I've been mentally designing what I think would be the perfect camera layout/design tool. I guess I will just list what features I think are missing from existing tools.

Open source, because that's how I roll.

"Heat map" style camera FoV cones, or at least shaded areas indicating DORI distances. Most or all of them just put a single color cone indicating camera coverage, but they just end at some distance and they don't give you any indication in the overhead view of what type of detail you might see.

Community-sourced camera specs. IPVM has a solid list of cameras, but I want an open system where anyone can add cameras. New ones come out every day.

And this is the big one, I guess a complete reboot on the whole concept: 3D modeling. There are free-to-use tools like DroneDeploy that make a flight plan to automatically collect hundreds of overhead and side view photos of a site, and they have a paid service to stitch them together into a 3D model or you can send your image set through free tools like WebODM to build your model.

Once you have a 3D model, you can place cameras wherever you want and simulate what they would see. Place and animate people and objects in the scene and determine the type of detail you'd get.

I realize that's a lot of trouble to go through for little added benefit for a typical residential system, but for larger commercial systems I think something like this would be amazing. Or if the workflow can be streamlined and simplified I think it would be an awesome tool for someone who does a lot of residential installs too.