That's incorrect. Don't heat empty homes, yes they take longer to warm up, but it's still more efficient to only year when you are around or incoming (which is where nest excels)
Having run nest thermostat for 3 years now, it paid for itself in 18 months in heating bill savings (around £10 a month), I can literally see the jump down in my online usage account comparing several years of data.
It's very smart about warm up and cool down times, and outside temps and forecasting z which is where there are huge savings to be had over dumb thermostats.
The nest protect fire/co2 sensors are also superb. They of course work as offline dumb sensors and are very loud, and have regular selfchecks, but also added online notifications if something is wrong. This is a potential addional life\pet saver...
Would I get a doorbell cam? Yep. Sounds like a good security addition, and evidence that delivery driver didn't actually ring the bell when they carded me..
Would I buy door locks? Nope, of course not. That's iot clickbait.