My experiences were with the McMurdo Dry Valleys LTER program [1]. They have (things may have changed) a number of sites sending telemetry back to the states via the Iridium network. Nothing too fancy. It worked. Biggest challenge really was that iridium was slow and relatively high power (and somewhat flaky deep in the valley where we were). I also had some involvement with the NTL LTER program[4], but that type of work has even easier telemetry constraints (these days, just use a cell modem).

I totally agree with you on the "using a combination of different sensors and a cleverly trained algorithm to get at the parameters of interest". This is something not too far from, in a way, how many sensors work already. They are *proxies* of the actual thing being measured. From my world, the s-can DOC sensor was always a good example, using in-situ spectroscopy to estimate DOC concentration.

Crux of the challenge is "what is the parameter of interest" and "can you come up with a way to estimate it with something easily measured?

Because this is HN, I'll say there is another interesting route possible. If you can change the economics of a situation and decrease the cost of a basic sensor, then you can often increase the volume of applicable uses. I was tangentially involved with the development of the miniDOT [3], which ended up being one of the first "inexpensive" (as in less than $5k) dissolved oxygen sensor. It really changed how people used them and increased the amount of DO sensing by probably an order of magnitude.

[1]: https://mcm.lternet.edu/ [2]: https://www.s-can.at/en/product/carbolyser-v3/ [3]: https://www.pme.com/new-products/minidot-usb-oxygen-logger [4]: https://lter.limnology.wisc.edu/