These little car-starting battery packs are awesome devices, and the Mycharge Adventure Jump Start is a great example, especially at the current $35 deal on Amazon. It's great peace of mind for a dead car battery or a dead cell phone.
Mycharge already has an excellent reputation for power products. The Adventure Jump Start is basically just a small portable battery pack: the same width as an iPhone 6+, not quite as tall and three times as thick. Let's just agree that it's small.
Features, however, are big. The 6,660 mAh Adventure will top off a big phone two or three times, a tablet once or twice, and it will definitely jumpstart your car unless you have a monster diesel that you're working with. The Adventure charges via micro USB, has a nice pop-out six-inch micro USB cable for charging other devices, and a normal size USB port to connect your own cables to charge other devices. There's a 4LED charge status indicator and even a small LED flashlight/strobe function.
Jumper cables are included, with six-inch leads, which is all you need because you're not connecting two cars. Just attach the red clamp to the red post and the black clamp to the black post and you should be good to go. Remove in reverse order. Fewer steps than jumping one car from another. And don't throw away the box, keep it for storing the Adventure in your car.