I'd recommend a cheap second-hand treadmill if you're going to try -- people are always selling these after shelling out a heap of money and realising that they mainly collect dust.
For anyone with a modern home that is sealed up average or better, an air monitor indoors is almost a must.
On the topic of the number of people and CO2, I'm tempted to have it alert me when I'm out of town and the CO2 rises. I have an alarm, but who would think to defeat the innocent looking air monitor on the shelf?
If it's vaporware on-device it's more evidence that it could have just been an app. Perhaps there was special on-device sauce coming in a future update, but as of now it's a client making http calls.
AI seems totally not like a giant bubble.
So it's not all useless.
Here's real-dollar food PCE. It's up about 38% since 2007 or just over 2% annualized increase above inflation.