A sequel to the company's successful FlameStower mobile charger, Stower's Candle Charger is designed to be used indoors for emergency power.
I'm a big fan of portable solar chargers for both emergency power and for off-grid charging, because today's mobile solar technology is reliable, efficient, and affordable. But they aren't perfect by any means. When it's nighttime or it's snowing or in the middle of a rainstorm, if you don't have a power pack or backup battery already charged, a solar charger is pretty useless until the sun comes out again (which is why I always advocate for adding a decent-sized power pack to your charging gear).
One possible solution for those conditions is a hydrogen fuel cell charger, which I got the chance to try out last year, but it didn't seem quite ready for prime time, both in terms of weight, cost, and the reliance on purchasing the company's fuel cartridges to power itself. Another fuel cell charger that I covered seemed to have the same issues in terms of cost and the need for buying new cartridges all the time. And in recent years, a couple of thermoelectric chargers have hit the market, mostly targeted to outdoors activities and backcountry adventurers, such as the BioLite stoves, but because they use an open flame, they are not intended to be operated indoors.
But a new entry to the mobile charging market, a "candle" powered charger (actually a Sterno-type fuel, from what I can tell), is designed to be used both indoors and outside, and could be one potential solution to keeping your gadgets charged during emergency power outages. The Candle Charger is a sequel to Stower's thermoelectric FlameStower, which uses a cooking fire or campfire to generate power, and the company is currently seeking funding and taking pre-orders on its Kickstarter campaign.
According to the information available on the campaign page, a single Stower Candle will burn for about 6 hours total, which is enough to supply two full iPhone (or equivalent) charges, and as a side benefit, will boil one liter of water (for safe drinking water) per hour during operation. The Candle Charger packs down into a little more than 4" tall by 4" diameter (10.16cm) for storage, and weighs in at 11oz (312g), so it's compact enough to fit into an emergency kit or bugout bag.
Assuming the device works as well as is claimed, the weakest point that I could see was its reliance on the company's Candle units to operate, which means that in addition to the Candle Charger, you've also got to stockpile enough of the Candles to make it through a power outage. I'd like to imagine that this device would also work with other 'canned heat' brands, such as those commonly available at outdoor gear retailers, or with an actual candle, but I couldn't find anything to confirm that (and of course, if your company sells its own proprietary fuel canisters, it's less profitable to tell people they can substitute another brand or heat source).
[Update: According to the company, "this will work with other liquid candles, like a Sterno."]