The iPhone helps with an endless number of tasks, but with a finite amount of battery life. So extra power is easy to find, whether it’s in an external battery or a battery integrated iPhone case.
But that battery is one more thing you have to charge. Strap on an Apple Watch and soon you are looking for a bigger bag that makes room for the charging needs of your various devices.
Portland-based Elevation Lab has a travel battery that takes virtually no room and can charge both your Apple Watch and iPhone a few times before it needs to recharge.