FYI on Fi there are many devices that seem to work well, even if they aren't on the official list of supported devices.
Fi also supports additional devices using a data-only SIM, which doesn't cost any extra except for the per-GB data rates. No $15 surcharge just for the ability to use other devices, etc. Same thing with tethering.
edit: also, this isn't exactly new, Google Fi was introduced in October 2016. I've been using it since then with no problems. In fact, I once received a reimbursement for a short outage that I hadn't even realized happened.
There's no extra charge for a data-only SIM but you are required to have a primary device which costs $20 (plus $10/GB). Would be great to offer this to customers on other carriers.
It's pretty cool. Google does not charge for the SIM so I ordered one. I think I'll pick up a cheap device sometime to keep on the boat for reading and use as a backup GPS!
I've been using Fi for a while but I didn't realize they had these data-only sims available.
I didn't know this was a thing. Is it new?