I'm guessing that the answer is a power monitoring plug but I wanted to see if there are any other ideas. I see the S31s are around 10 bucks each. All I want to do is tell when one of my several heat tapes on my plumbing turns on and off. I have a bunch throughout my old house so that's why I was trying to see if there was a simple/cheap way to do it.
#What's the cheapest way to tell if a device has turned on?
plucky rose
vast juniper
as you suspect, a smart plug is probably going to be your best option.
lusty wharf
In your case you could perhaps also use a hygrometer. My preference would be a power monitor because the power/energy usage/consumption would be interesting to me and because I'd use a zigbee device and more routers are helpful.
proven juniper
🤔 that would be interesting data. the areas needing heating most often would also be most in danger of freezing in a power outage, so prime candidates for more insulation .
depending on how those heat patches are wired a microcontroller with one or more current sensor clamps could also work. but those clamps must go over a single wire.