I've gone through several backup battery solutions over the past few years and all suffer from either a lack of power or were ridiculously large.  The iTorch has in the short time I've owned it proven it's worth.  I've recharged my Nexus 4 from 14% remaining to full and then topped off my Nexus 7 from 36% with no issues, then had a friend ask if she could borrow it, allowing her to get a good extra bit of charging on her iPhone.