Here's a very cool gadget that I backed via Kickstarter, and have added to my mobile power ensemble. I've previously covered power generating thermo-electric systems such as Tellurex tPod1
and the bioLite power generating campstove as well as some options for going solar.
I've also covered a couple of power units, such as the Snow Lizard SLXtreme-5 iPhone case and the Power Travellers Power Gorilla.
This is the Practical Meter which is a clever little in-line USB unit, which gives you a visual means of determining the power usage and output. The LED's built in give an indication of the number of Watts (0-10W, 0-2A) that is being drawn to a given device. This display is in two stages, blue LED's lighting up for 1-5W, and then with the flashing red LED indicating 6-10W.
This level of resolution enables the user to customise the output, either by adjusting cables for better USB version, or the power source. For example, with solar collectors, it would be possible to adjust the angle of the panel to catch the maximum solar output. The same would stand for a thermo-electric generator, or any USB source combination.
Having an adjustable and monitoriable source of power means that a survivor can tailor their resources to best serve their needs in the event of being cut off from reliable mains power. Whether it is solar, fire or from a variety of battery sources, with an item like the Practical Meter, you can at least see what you are getting. It's not a robust piece of tech, so needs to be treated with more care than a ruggedised piece of bug-out kit, but at 12g (0.4oz) it's a great value piece of tech to add to your "power-pack pack".