[cvp]

The v1 devices never supported a real local API. The v2 devices like the Awair Element do have a local API built-in. It does have to be enabled via the app but it lets you hit the device's LAN address and get back real time JSON with the sensor data. Not to say they couldn't figure out a way to brick those devices in the future, but you could theoretically turn on the Local API and then firewall the devices to your network to prevent future firmware updates.

[zapt02]

That would work for a while but if you ever needed to set it up on a new Wifi network you would be screwed, as the app is required for initial setup.

[TeMPOraL]

One thing I've learned over the years is that it's good to "own" your SSID, and preferably stick to pro-grade routers that let you configure local network addressing. As long as you stick to Internet providers that let you run their hardware in "bridge" mode, it means you don't have to set up new WiFi networks at all.