Update: I have received confirmation that your data between your cellular/data SIM and your data SIM are pooled. So if you have 5GB of data, that is your plan for both devices.
Update 2: It looks like the vast majority of Fi users can now order the Data SIM. Just go to Accounts>Your Plan and you can add it to your plan.
The Project Fi team has announced that existing customers will be able to start ordering data only SIMs for a select range of devices as soon as today. It is something many have been waiting for from the service and once your SIM is ordered through your account, you will be able to use Fi at the same rate you do on the cellular/data plan: $10 per month per gigabyte used. Google has published a coverage map which is available at this link so you can check the data coverage area in your area. This coverage map is good for both cellular/data Fi users as well as data only users.
Existing Project Fi subscribers can order their free data-only SIMs from the “Account” page on the Project Fi website. This change is rolling out gradually, you should see the option to order data-only SIMs sometime in the next couple of days.
I have reviewed my account page on Project Fi and I’m not seeing the ability to order the SIM just yet but I will update this post once I see it has rolled out as you too can keep an eye out for it.
If you are curious about Project Fi, you can read about my experience with the service including my travels here in the US.
Project Fi Data Only SIM Compatible With A Small Number of Device
Given that Fi is still rolling out itself and still considered an early adopter program, the number of devices compatible with the data only offering is pretty small at the minute.
- 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
This list I suspect will change over time as more compatibility testing is done but the good news is you don’t necessarily have to have a Nexus device to use the service.
Finally, given that you are adding a SIM to your existing account, I am assuming although it is not clear. I have asked for clarification on this and will update the post once I hear back from the Fi team.