For example, I have my home office in my basement. I have an automation in Home Assistant that when I turn on the Z-Wave light switch at the top of the stairs, it turns on my desk lamp and recessed lighting, and if it is a weekday during work hours, it will send a wake on lan packet to my work computer.

Another example, I have a tilt sensor on my garage door, and a contact sensor on the door into the garage, so that when either of those are opened, the main garage lighting turns on.

There are also odd niches. I have an air compressor in a far corner of my shop (for noise reasons) with pipes running to where I need air. I want to control that without having to walk across the shop. (So far I don't have this because finding a switch that control a multi-horsepower induction motor is hard - most top out an 1/4 horse)

* schedule my non-smart EVSE to charge our car when power is cheaper at night

* monitor (but not control) the energy usage of our electric hot water heater. It's the second biggest electricity user in the house but I have to infer how much power it's using based on the other separately metered components.

Cost is the thing holding me back. Will it have positive ROI in a reasonable time for our PHEV minivan that only has a 30KWh battery? Seems somewhat unlikely. Would monitoring the power usage of the hot water heater have positive ROI ever? Also seems unlikely.

At my first job, I worked for a company that built (among other things) X-10 powerline-control interfaces that would let your PC do the same thing: switch on lights/fans, etc.

As far as I could tell, the only people buying that stuff were hobbyists with a lot of disposable income. Part of my duties was customer support and I can't recall a single instance of anyone doing it for any reason that didn't boil down to "it's cool."

Not making judgements, but I really don't see what the big deal is with getting up to turn on a light, and I live in a pretty big house.

But an optocoupler relay is also about £1, so there's that.

But things that can use it seem to be expensive. I checked, the chips are fairly cheap; but all the PoE stuff I might use aren't "one per light socket" prices. Plus I'd still like a decent mains relay board that is appropriate to put in a wall - the Shellys' are a good form for this, but I cannot see a similar wired solution (although some Sonos devices get close).

But I'd sooner order from a company that is liable e.g. if the IoT device burns down my house.

If your IoT device burns the house down your circuit breaker failed, or you connected it without proper failsafe measures.

Is it burning it down by being on fire itself, or by turning something on that shouldn't be?

If the thing just heats up and catches fire, it might not trip the breaker. I meant overheating itself, not erroneously turning things off/on.

Having one switch control all your table lamps, floor lamps, and ceiling lights is useful. Being able to add new wall switches (really remotes) in new locations for ~$25 also nice (excluding the cost of the rest of the system, obviously).

A few years ago, we had no switches or light sources by the entry way; we had to stumble our way to a switch in the dark. I fixed that with remote controlled outlets at first and later upgraded to Hue bulbs and dimmers. In the bedroom, my wife and I both have remotes for the lights (though she actually prefers voice control, ironically).

We have a few useless wall switches that control outlets instead of lights; turning those into in-wall remotes makes it so we can control multiple lights and use the outlets for devices that need continuous power.

We also have our light bulbs automatically change brightness and color temperature based on the time of day. We get daylight-bright light during daylight hours and dim warm light in the middle of the night. It's really nice.

Another nice smart home feature: checking that the range is off. My wife used to stress about this, it's no longer an issue. Don't worry, you can only turn the thing OFF remotely, not on.

The smart speakers are mostly for music, checking the weather, and time. Occasionally for light control.

Smart/energy monitoring outlets we use mostly for tracking down energy hogs and reducing our energy bill.

The security and privacy stuff is a risk, but as long as you stick to major brands IMO the risk is overblown. Those brands are subject to a ton of scrutiny. Fly-by-night alphabet soup brands off Amazon or Alibaba are another matter.

1) Motion sensors

* Our hallway lights turn on via motion and turn off automatically.

* My work desk lights turn off and on via a motion sensor.

Both apply the correct color temperature and brightness based on ambient light and the time of day, so that I don't get blinded buy 1100 lumen lights at 5000K when I go play a few rounds of $game at my desk.

Just having the bathroom lights turn on and off automatically is magical.

2) Voice control

We have a few Alexa routines programmed for the house:

* "Movie time": All lights off, TV and AppleTV turn on

* "TV Time": TV off, few lights near the TV turn off

* "Good morning": Lights at a reasonable level, Alexa tells us the weather forecast and traffic (well not anymore, we work remotely).

...and a bunch of others.

3) Wireless switches.

All of the above can be controlled via physical switches mounted around the house where practical - not where the wiring happens to be.

I've got a whole home full of these, switches and bulbs and smart speakers. They do some very useful things for me:

* Turning the lights on before entering a dark room with inconvenient switch placement inside

* Ensuring all the lights are off before leaving or going to bed

* Turning on my porch light when it gets dark, and off again in the early morning

* Simulating liveness when away on vacation

* Turning the lights on when I've got my hands full of grocery bags

* Ramping my bedroom lights up slowly in the morning as a gentle wake-up

* With some cheap motion sensors, ensuring that lights that are often accidentally left on are turned off, saving power and money.

I'd rather have a 2-way light switch at either end of the hallway and hit a switch when I walk down it, rather than program in every exception like "turn on the hall light when it detects motion unless it's 3 am and I'm walking to the bathroom to pee, or if it's 3pm and my girlfriend is napping on the sofa next to the hall and I don't want to turn on a light and wake her, also ignore cats triggering the motion detectors." My small apartment with regular old deterministic switches is fine. I had a Nest once and hated it. At least for me, the ideal temperature for a room must be a very subjective and non-rational desire. Sometimes I want to blast the heat, sometimes I want to feel cold, it's probably emotional/psychological on a level that Nest can't model.

I know someone will point out that 100 years ago I would think washing machines sounded ridiculous because I could scrub my clothes by hand easily enough. That might be true, but I would counter that there are diminishing returns on home automation. Indoor lighting was a massive improvement over living by daylight hours. Electricity over gas was a big improvement, but not as big as going from dark to light. Turning lights on with Alexa, to me, sounds like the benefit/cost curve has plateaued.

For example, when I come downstairs and say “computer lights on” it’s easier than flipping two switches and turning on two lamps.

Both android and iPhone have voice control so if you have a smart phone you have capability for voice control, you just don’t use it.

But the phone home stuff is just insane to me. I bought an Insignia garage door opener trigger that works with Homekit natively without an app, figuring that would be the simplest possible setup (and cheaper than RF-based physical remotes). I Wiresharked the traffic it was sending out (in order to block it) and it phones home over a *Wireguard VPN tunnel*. I've seen some shady phone-home behaviour from cheap Chinese devices but never this.

So now it is totally blocked from accessing the internet and it does open the garage door, but I am told "there was an error communicating" every single time.

I will mention one device I absolutely love: CloudFree Smart Plug 2 for energy monitoring. As I mentioned on my Twitter※: [CloudFree Smart Plug 2] are the first IoT product I've ever used with zero friction whatsoever. First time usage, from unboxing to pulling power stats over HTTP API in under 3 minutes. No other products come close.

※ - just copy/pasted my Tweet, no need to hyperlink it

I could open it and connect more stuff to the GPIO, patch out the annoying LED or do something else with it. Install tasmota instead. It's quite liberating :)

I also use Alexa to set reminders, get Roomba to clean specific rooms (or the whole house) and I use it constantly to control Spotify.

You can argue that Alexa is spying on me or whatever but i'm not sure how that's worse than the iPhone I carry in my pocket literally everywhere I go...

Don't know if I would use the adjective "smart" compared to a switch.