A Project Fi support page for tablets and "other compatible devices" has just gone live, and it spills all the juicy details of the very-soon-to-launch (we assume) feature on Google's MVNO. The best part? The money: it costs nothing to add a tablet to your Project Fi plan. There is no monthly device fee, and it doesn't even appear that Google is charging for SIMs, though we've yet to verify that. You just pay for the data you use, and that's it.

You can add up to nine data-only devices - be it a tablet, smartphone, or something else - to your existing Project Fi voice plan this way, and Google has provided an initial list of hardware that it deems compatible.

Nexus 7 - K009 (US LTE)

Nexus 9 - 0P82300 (US LTE)

iPad Air 2 - Model A1567

iPad mini 4 - Model A1550

Galaxy Tab S - Model SM-T807V

The support page says that other T-Mobile-compatible GSM unlocked tablets and other devices could work with Fi, too, and invites subscribers to order a SIM and give it a shot if they're not certain. Setup is as simple as popping in your SIM and entering the appropriate APN information. One rather annoying note is that tethering is not supported with data-only devices on Fi.

Instructions on the page state that ordering a SIM requires going to the Project Fi website, entering the account tab, then going to "Your Plan," and selecting "Add data-only SIM." You can read the official announcement on the Fi forums here, in which it's stated that the option to order data-only SIMs should be rolling out to all Fi subscribers over the next couple of days.

We're also asking Google whether or not the T-Mobile/Sprint network switching is supported at all on data-only devices, as many of the devices in the list above do not work on the Sprint network. Based on language on the support page saying that T-Mobile compatibility is what users need to look for when adding a data-only device, it seems possible that only the T-Mobile side of Fi is active on these data-only SIMs, but we can't be certain.