I picked up one of these as I needed a portable, high-ish capacity 12v power source. Looked around at a variety of car/boat batteries, and anything close to this capacity (38ah) was close to or more than $200, plus I'd need a charger.
This unit is obviously a car jump starter, but it has dual 12v accessory ports (cigaret lighter styler), a work light, battery meter, and a a USB port on the back PLUS it has it's own charger.
Pretty compact for what it is, albeit somewhat heavy. These are great if you have troubles with the car, or want some redundancy if you're going travelling or camping. I personally just use it as a good power source for 12v accessories that I can run for a long time.
Just make sure to keep it charged as per the 3 month cycle in the manual, or it will die
Sorry, I forgot to include it in the title - but it's obviously from Supercheap Auto as it's their own brand