The trouble with the Palm is that it's not that great of a phone. While the $350, Verizon-exclusive child-sized device is nothing if not adorable, its incompatibility with iMessage, cramped keyboard, and poor battery life makes it a pale substitute for the bigger device you already know and love. Mophie's juice pack will add another 13 hours to your tiny Palm's battery life, so maybe, just maybe, it can survive longer than an adult mayfly. And the rechargeable case is small enough that it won't add too much heft. The mobile powerstation doesn't attach directly to your phone, but it comes with a keychain, which allows you to hang it off your backpack or purse and it has an integrated USB-C cable for charging.
By itself, the credit-card sized "companion phone" that is just begging to be lost down a public toilet has a battery life of seven to eight hours. That is if you don't browse the web, check email, watch videos, or do any of the other the basic tasks a smartphone is supposed to do. If you do use your Palm to catch up on work emails or watch videos while waiting for the train, you're looking at a 2-3 hour battery life, tops.
Despite its drawbacks, there are likely some adults whose lifestyles will be benefited by a secondary mini-smartphone such as the Palm. And if you're in that group and don't want to risk it dying on you while you're on-the-go, there's now help.