Xiaomi might have what you are looking for: https://www.aliexpress.com/item/32966216308.html. It's zigbee, multi-year battery powered, costs $10-15, does temperature and humility. No soldering, programming or any other diy.

You can get a zigbee radio that can serve as a hub for a few bucks, but if you want the turnkey consumer experience, you also need Xiaomi's zigbee hub which runs around 50 bucks. With that you also get an iOS app that integrates with homekit. Xiaomi makes a lot of other zigbee products at a similar price range that work with it.

You're not going to find any acceptable wifi solutions in the battery powered sensor category (there are a lot of other reasons that make wifi non-ideal for this), so unfortunately a hub is probably in your future for any option.

EDIT: BTLE devices may also be an option, but IoT applications my tldr option is that BT is too complicated to be worth it unless you need something you can't get elsewhere.

I have a bunch of Xiaomi zigbee sensors (door/window, temperature, and water leak) connected to my SmartThings hub -- You just need to install a device handler and they will work fine (though from what I've heard Xiaomi devices don't work well with most repeaters -- these are pretty much my only Zigbee devices so they are connected directly to my hub and work great).

I don't trust Xiaomi for anything connected directly to my network, but zigbee devices connected through something that I (kind of) trust works for me.

I run a company (https://flair.co) that builds a device you could use but is admittedly out of your proposed price range. That said, it's consumer/prosumer grade and you can network as many as you want together. You need at least one to be wired so it has enough power to fire up wifi and the rest can be run wired or on batteries. They mesh over a 915MHz radio and temp/humidity/light/pressure. We have been contemplating building a cheaper headless unit (these have a fancy little E-ink display) but haven't done it yet.

The actual device is here: https://flair.co/products/puck

There is a full fledged API (api.flair.co), desktop (my.flair.co) and apps of course. For what you are looking for, there is plenty of plotting built in but you can also export the data from the app as a csv/spreadsheet or grab it from the api.

Anyhow, it's definitely over your targeted price point but functionality wise, I think it does everything you might want.

As a consumer wanting a better HVAC solution, I've been following this space for years and am glad to see your company still here and offering products for sale.

I think there is an opportunity to grow your market if your Puck (or a new kind of Puck) can incorporate air quality sensors and make the data available. If you go this route, please see the recommendations in this comment as accuracy is key (https://news.ycombinator.com/item?id=20642939). I would certainly purchase multiple Pucks if they provided accurate data in a format that I could query myself if I wanted (no subscription BS please). People are concerned about air quality yet have no easy way to accurately measure it in their homes.

The bonus is that if I've got Pucks already, I would be more likely to purchase your Smart Vent products.

I also haven't found anything commercial in this space. Luckily it is a pretty easy and cheap (<$10 in parts) hack project.

I made a thermometer/barometer/hydrometer using an ESP-8266 wifi microcontroller ($5 on ebay) and a single BME280 sensor ($1 on ebay). Plugged into one of my left-over old 500mA phone chargers, it makes a wireless indoor weather station that speaks HTTP.

I bought the sensor on a breakout board, soldered a couple of wires, flashed micropython to the ESP-8266 (NodeMCU), and wrote wrote Python to POST my server with the temperature data, schedule a wakeup, then go to sleep.

But as you say, it took me a weekend of hacking around to build. This seems like exactly the kind of thing that should be available for $10 on eBay yet I can't find anything at all open.

I bought a bunch of wireless temperature/humidity sensors from AliExpress - they broadcast their readings once a minute via a small 433Mhz radio-transmitter.

Completely standalone, no WiFi, or other concerns. And because they're battery powered I think they're safe enough in the sauna!

From there I can get the readings via a USB-attached SDR dongle, and also sniff the radio-transmissions via a WiFi connected ESP8266 device with a radio-receiver.

Xiaomi Aqara temperature and humidity sensor.

* Under $10.

* Works with zigbee.

* Works out of the box with open source zigbee hubs. I personally have conbee II/deconz.

And the whole setup of these open source zigbee solutions usually just consists of plugging in the USB device and starting a docker container. It's not not the tedious open source setup as it often is with open source projects.

As a bonus you can use different zigbee devices from different manufacturers all together.

Thanks, sounds perfect, I'll try that.

I used RuuviTags (https://ruuvi.com/). They use a battery and send data over Bluetooth to your mobile phone.

You only get data from those when the phone is in bluetooth range. That's not very useful for long-term measurements. Unless you buy cheap android phone as a basestation I guess.

I have a bunch of SensorPushes at home which do the same, but they store the data for up to 20 days iirc, so it's effectively continuous data unless both my wife and I go away for a month or so.

It's popular to set up a Raspberry Pi or similar to act as a bridge between Bluetooth and wifi.

Agreed. Having to set up a raspberry pi or some other microcontroller is time consuming and the end product is ugly. I would like something small that connects to WiFi that operates off battery or could be plugged in permanently.

I recently purchased Wyze's sensor starter kit and have been quite impressed. The contactless sensors are tiny and have decent range to the corresponding bridge. Now Wyze just needs a documented, public API.

Pimoroni made this quite easy though if you know a bit of python https://shop.pimoroni.com/products/enviro-plus

Small and WiFi sound like an ESP8266 could be right for you. Or a Wemos D1 Mini, which uses an ESP but comes with a USB port.

Have you seen these remote temperature monitors from sensorpush? They seem to do a decent job and there is an internet gateway device to manage them if you want.

http://www.sensorpush.com/#products

I use xiaomi to measure temperature, and send it to homeassistant.