Power packs

[ModMan]

Does anybody know much about these external battery backups? I've seen this one which is highly recommended which can jumpstart a motorbike a few times, charge USB devices and even laptops with it's 19v output and multiple nibs:

http://themicrostart.com/products/micro-starts/ Specifically the XP-1 and XP-10

But then you come across the usual Chinese ones like this:

http://www.ebay.co.uk/itm/311243496908?_trksid=p20...

It has a much larger mAh value (30,000 vs 18,000) and almost all the same things for around a quarter of the price. I'd use it really for charging external USB devices (Tablet/GoPro etc) and as a backup to jumpstart my motorbike when out on my adventures in the middle of nowhere, literally.

Any advice or opinions of these or alternatives.

[ModMan]

Thanks, I'll check out the other options. The Antigravity one has great reviews and demos of it starting cars and motorbikes. Looks like I will lean towards it as I don't fancy exploding batteries in my panniers!