[xnyan]

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.

[kiseleon]

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.