For backpacking you of course wouldn't want anything like this, though I do sometimes carry a small USB power pack if I want to keep a phone charged.
I also camp in an a-frame camper, often off the grid. The camper has an on-board battery, but I'm usually also powering a laptop and astronomy equipment.
One of the pictured units would probably work for me, but for a cheaper solution I use a deep cycle battery. It's in a plastic battery box (like you would have on a camper for for a trolling motor), where I've added fused 12V power ports (power poles and auto DC sockets) and a volt meter. It's heavy, but lasts a long time.
I recharge both the camper and battery box using a 100W solar panel and charge controller. I just hook it up to whatever needs charging for the day and leave it out.