You found a bad user experience for you (a problem) You built an e-doorman (a product)

Now think about the problem an solution in terms of Product and market

Is the market who you think it is ? (I.E. who will buy this ? people, buzzer system makers or building owners ?)

Then think about what would be the product that would allow your market to solve the problem. Might not be the one you built exactly.

A product is only successful if it solves a problem for a market. Both problem and market are mandatory.