[wlesieutre]

And what's the initial plan cost to get that shared data pool?

I pay $30/5GB (then throttled unlimited), so if I have to switch to a $50/month plan for a shared pool and add another $10 for a second device, then we're up to $360/year.

[MBCook]

I'm assuming the plan is a sunk cost because I already have the necessary one for my cellphone.

The only question for the watch (or any other device) is the additional fee for that and any extra data I might end up needing.

I think the fact that it cost $20 to put my phone on the network (not including any data costs) is already stupid. But it's too late there.