The Yellow Jacket Defender is perhaps the most interesting piece of iPhone-related self defense equipment I have seen to date — not because of its function as a 650,000 volt stun gun, but because it acts as an external battery pack, which is something that would prove useful on an almost daily basis.

The downside, it makes your iPhone an inch thick and doubles its weight – a small price to pay for an extra 20 hours of battery life and the ability to temporarily incapacitate a physically superior foe.

Price: $80 while it is up for funding; $100 thereafter. [Source]