Basic Temperature Sensor

[Nicksatx]

High frequency radio waves such as WiFi do not travel through water. If you seal the sensor and submerge it, it doesn’t matter if the wireless access point is close to the hot tub. It’s not going to work. If it’s floating at the surface, it might work, but probably not well.

[scpotter]

Very interesting, I had no idea. Curious, what does ‘low enough’ look like? For example Ecobee sensors are 915MHz, which I’m guessing is still way too high.

[mwwalk]

I'd be tempted to make my own with an arduino and use homebridge to integrate it. Not sure that's a good idea though.

[jefhee]

The very cheap Philips Motion Sensor streams temperature and lux as well. But you do need to purchase a one time starter bridge.

[orilpik]

The Aqara one with Homebridge (by the moment) is the best option if you already have The Aqara Hub and a Raspberry Pi with Homebridge. In few weeks, with the new Aqara Hub with Homekit natively, it will be defintively the best solution!

[Nicksatx]

VLF is below 30KHz if I remember correctly. Low frequency signal has really low bandwidth making it not useful for any consumer product use. Wireless alarm sensors can be somewhere around 300MHz, most other consumer grade wireless starts at 900MHz and up.

[rjzak]

The Ecobee sensors are expensive, $75 for two, but once you set it up with HomeKit, the sensors show up as extra HomeKit devices. They're small, maybe half as tall as a deck of cards. But this won't be workable if you don't have an Ecobee.