Have a bit of experience in this field, on a technical side:<p>- Always provide a way to auto update and fallback if failed.<p>- never implement a buzzer or beeper.<p>- stay away from blue status leds. people really dislike them, especially in the bedroom.<p>- always design with sleep/low power mode functionality. If it's embedded uC: 1 watt is more than enough, even with RF. Pick bistable relays. If it's a Linux SoC aim for less than 3W. If there's wifi keep it under 21 dBm. Pick sps modules like 78SRxx from murata instead of linear 78xx.<p>- if it's a thing you plug in the wall socket make sure it doesn't obstruct other sockets.<p>- expect people to unplug it every moment every day.<p>- don't force people to provide an email to activate some functionality or feature.<p>- use open source standards for communication protocols and put yours in a public datasheet with detailed info on how to parse & process.