[robmcm]

Why not use a usb battery pack for your phone? Seems like one fewer thing to carry, and no extra 4G cellular contract.

This generally seems to be my conclusion when thinking about making something cool with a Pi or similar, wondering if I’m missing something?

[cweiss]

It's a fascinating idea. The Pi Zero is tiny (likely much smaller than the battery pack). I'd think it's not that big a deal. Plus, depending on your employer, they may have unreasonable requirements for subsidizing a phone contract vs a 4G stick.