1. For a Linux user, you can already build such a system yourself quite trivially by getting a kaggle account, learning by doing computer vision projects, and then using opencv to build the vision parts of the system. From Windows or Mac, you could build using a cloud system such as Amazon Bedrock.
2. It doesn't actually replace having a hat for the period from your own front door to OP's apartment. Most people I know own hats themselves or borrow from friends to be able to attend specific events, but they still carry a hat in case there are weather problems. This does not solve the availability issue.
3. It does not seem very "viral" or income-generating. I know this is premature at this point, but without charging users for the service, is it reasonable to expect to make money off of this?
[1] Actually I don't. It's really awesome.