This feels like a dumb question, but I can't find dimensions of the Notecard anywhere and I can't quite judge the scale from the pictures. How big is it?

https://github.com/blues/note-hardware/blob/master/Notecard/... has the measurements, looks like 35mm x 30mm

Keep in mind that’s he card with a M.2 edge connector on one end. Mostly you’d be plugging that into something, at least to hook up the power/data lines. They sell “Note Carriers” for that, which end up making the combo bigger than that.

Here’s a pic of the note card plugged into their Raspberry Pi note carrier. That’s a standard 40 pin 0.1” spacing connector on the left, so it’s 2” plus the mounting holes in that dimension. 65x57mm and about 20mm tall for the stackable 40 pin socket+pins.

https://flic.kr/p/2mkQAS7

What service are they using that gives 10 yrs of connectivity for a flat price?

It's not 10 years of unlimited data. It's 500MB of data usable over 10 years.

Probably "VC Cash".

I've got a couple of the units and can say they are working well and very easy to interface with.