The JunoPower JUMPR looks like a lot of other backup batteries we've reviewed and it does a great job charging your tablet or smartphone. It aims to justify its $99 price by also coming with a pair of custom jumper cables that you can use to start a car with a dead battery.
Carrying a portable battery charger takes up a lot of space in the trunk and lots of people hate dealing with regular jumper cables, plus they're not much good if you're stranded in a remote location and there's no one around with another car.
It just so happens that we had a dead battery at my house this week and got to test out the JMPR in real-world circumstances. It's easily charged via the micro USB cable (a lighter cable is also included) and then plug in the jumper cables and hook them up to the car. With a completely dead battery, the JMPR started the car on the second turn of the key.
It doesn't take up much space in your tool bag and, as long as you check the charge every 3 months, it should give years of peace of mind for anyone in your family who might get stranded on the side of the road.
The charger has a 6000 mAh batter that offers up a 12-volt, 300-amp output. It's enough power for 4-and 6-cylinder engines but it's not designed for and probably won't help you start a V8. The whole kit comes in a great box that makes it a nice-looking gift and the battery is available in either blue or black.
That's a reasonable limitation on a device this small. And, to be clear: the JMPR is going to give you just enough juice to get your car back on the road. It's not going to charge a dead battery. As an emergency backup device, however, it's a great tool to have in your car.