The Bracketron SmartLantern combines a 7800mAh rechargeable battery with a 64 lumens combination lantern/flashlight and sells for a $79.95 list price. It weighs just under a pound and it's about 5 1/2" high.
Obviously, you can get a high-powered LED flashlight that runs on AA batteries for $5 and there are a lot of backup batteries out there for less. What's the attraction here?
First, it's a high-capacity battery and should provide at least four full charges to your phone in an emergency. If you're not charging, it can provide up to 48 hours of light from the flashlight (when the SmartLantern is collapsed) or the lantern (when it's extended). At the top of the list is this: it should hold a charge for a year, so you can charge the device and have it in reserve for a crisis.
It comes with a wall charger, a Micro-USB cord for charging the lantern and a carry bag. If you're an iPhone user, you bring your own lightning or 30-pin cable. The hook on the top makes it easy to hang from a car hood (see above) or a tent pole or a nail in your garage. It's light and small enough that it makes a good backup for a long hiking trip and the high-capacity battery gives you extra power if you want to be prepared in case the grid goes down for a few days.
You can find a discounted price if you look around online. Ignore any negative reviews you might find out there: the SmartLantern works fine. You just have to push the button next to the plug to direct power to your phone.