I've been thinking of designing my own smart devices, but they will need to fall back to simpler devices. For example, I want to build a smart lock that unlocks

I've been thinking of designing my own smart devices, but they will need to fall back to simpler devices. For example, I want to build a smart lock that unlocks with a GPG key on my phone, but still has a key (bolt on motor to existing lock). I just don't understand these smart devices. At best they're marginally more convenient, but they come with a lot of risks. I'm worried about software not getting updated, data in the cloud being compromised, or simple loss of function from not degrading gracefully. My smart TV is nice because it has Netflix built in, but nothing else on the market is interesting to me.