IoT chips are expensive. In working to drive down costs around multi-part products, such as a smart doorbell with its speaker and button combination, we engineered Aeotec's Doorbell stack to utilise a combination of inexpensive 433 MHz and Z-Wave. The first generation wasn't the best work we could do, but the second iteration really improved upon it and has been awarded its utility patent today. I'm a co-inventor on this. I'd like to revisit such a product again in the future - I'm sure that the perfect smart, cameraless doorbell is yet to be engineered.