Stationary smart devices should not require battery replacements. Batteries make plenty of sense for mobile devices or as an option for people who view aesthetics over any level of practicality, but all stationary devices should have the option to be wired into wall power. Most battery-powered IoT devices claim to have battery lives of 6-24 months, but in my own testing, their lifespan is closer to 3-6 months. With dozens to hundreds of devices per smart home (a conservative number if you believe all homes will be reasonably automated in the future), this means at least one device will have its battery die every week, or in some cases, every day. While replacing batteries twice a year is not a major nuissance, these devices will have their batteries die at different times, creating a weekly chore to find obscure coin cell batteries and replace them in the right devices, and breaking automations for multiple days each week. Most people I know just give up when their smart home devices stop working, and live for months with dead batteries (I am sure security companies can validate that motion sensors and door sensors often go months or years with dead batteries before they are replaced).
So what is the solution? Simple: add the option to charge via USB. I have been fortunate to find motion sensors that allow for continuous power via USB (which also allows them to act as repeaters, improving network latency and reliability), and at least one smart button that offers continuous USB power. I've been able to get almost every smart device in my house wired into power except for my automatic IKEA blinds (and their corresponding controller buttons). Their blind controller buttons can only be powered by coin cell batteries, and although the batteries on the blinds can be charged via USB, the frame blocks the port when installed in the blinds themselves. I have had to replace these batteries countless times, and I had enough: it was time to hotwire them into USB power.
The blinds were the easiest to power. I disassembled the blind power system and used my Dremel to drill holes in the frame to allow a cable to pass through. The fit was tight, so I had to buy some aggressive right-angle USB cables so it could fit. Reassembled, it looks good as new. To help preserve battery health, connected the USB chargers to a smart switch. The switch turns on at midnight (when power is least expensive) only when the battery is below 30% charge, then turns off at 6am.
The buttons were a little more difficult to work with. Coin cells operate at 3V, so I needed to get a 3V continuous DC power supply to them. USB seemed a reasonable option. Using disassembled USB cables, I identified a 3V wire but realized that the voltage would drop to 1.7V when under load. Fortunately, the buttons could handle the 5V wire perfectly fine (most electronics have some tolerance on voltages they can work with). I then soldered the cabling into the battery contact points and used my Dremel to cut a small hole in the plastic frame for the cabling to come out.
I then mounted my first two buttons onto a control panel on my desk. As I buy more cabling and parts, I will mount other buttons on the walls and add cable covers to hide the USB power for the blinds and buttons.
Here I have the first version of my desk control center using a rough cut of particle board to mount the first of my control buttons onto.