... Interesting device, but until the cost comes down, I just don't see it gaining traction.
I do. I have had battery jump packs for a long time. They are handy, but like you say the size of an automotive battery. They need to be maintained. Periodic charging is required.
What makes these better?
Smaller in size and weight. I can stow it under my back seat, in the glove box, on the motorcycle, heck even in my back pocket. Fits right into the pocket on my solar panel case. Perfect for my BOB.
Holds a charge a very long time. It is advertised to hold full charge for a year. That I can not yet attest to. Not having to charge more than monthly to maintain is an advantage.
Multi-functional. 5v charging for cell phones with every possible adapter included. LED Flashlight. Laptop charger. Jump start the vehicle. Run my fridge in a pinch.
Cost. I will grant you that they are on the upper side, but not when compared to a fullsize AGM battery, or a good size jump start pack. I think they are in the right price point.
I do have two fullsize batteries in my truck. I can still justify it for running the fridge. I am not sure I would have installed the second one now that this is around. I might have risked my starting battery. It builds lots of confidence to have the lithium jump pack and solar panel
Now that I have had one , I am seriously considering another for the wife's car. Peace of mind for both of us.