I think multitools exist so that my flashlight *doesn't* have to have anything come out of it. [emoji51]
Doesn't have to no, but that means you are carrying around a potential power source you cannot use for anything else but light. What a waste if you need a phone function while out on foot somewhere and cannot access it because your battery is too low, yet you have a fully charged 18650 sitting in a rugged compact enclosure in your pocket or on your belt, that you cannot use for anything but light, when the circuitry required to add the powerbank function is so small you could probably fit several in a matchbox.
How does your multitool help you with that?
Doesn't that seem like a function flashlights are ideally suited for?
Your other common pocket EDC items cannot help with that (Wallet, phone, keyring, watch, multi-tool, pen)
The closest I have seen is an effort to make a credit card profile power bank, apparently they don't work well and who wants that in their wallet, we carry too many cards as it is, I have 17 credit card profile items in my wallet right now, and only 2 of them are credit cards.
In fact I would go so far as to say that it is specifically the lack of this function that makes the flashlight an uncommon EDC item compared to the above.
There must be other functions in the same bracket, that the flashlight is uniquely well suited for.
You know, if backup power is adopted as a flashlight function, then there are several other EDC items that need backup power which could benefit, not just your phone:-
Right now I have a USB chargeable Polar M400 running watch on my wrist
The heart-rate sensor uses a lithium 2025 coin cell, which would add almost no size and weight to an 18650 flashlight.
I have 2 gate remotes (work and home) an alarm system remote (work) and a car remote on my keyring, all of which use the same small battery that would fit in an extended tailcap of an 18650 flashlight easily, remember how the maglites carried a spare globe?
I have a small AAA keyring flashlight, that could be replaced by one of the increasingly popular 10180 lights with micro USB charging built in.
It all adds up, a flashlight adapted to be a custom backup power source with modular fittings could become an indispensable carry.