That jump pack is no joke. Recently had to start a Corvette with a tired 6.0 liter V8. Tried jumping from the winch battery I had on hand...click. Remembered I had this little guy under the seat. It fired like day it was made.
This reminds me of a device I have in my office at work left behind by my predecessor, I've not had occasion to use it just yet though. From what I can tell it is designed to charge a dead 12v battery from a wall socket though I'm guessing it would jump one too if you could get the machine close enough, it is Husqvarna made.