Your iPhone is an invaluable resource in a survival situation. The survival application go even beyond the survival tactics you learned playing Plants vs Zombies. With these pieces of hardware, you can turn your phone into  full-on SHTF gear. 

Polismart Radiation Detector continuously monitors radiation levels and wireless transmits them to your iPhone. Designed for professionals working around gamma radiation, the free app is easy for anyone to use. 

Yellow Jacket Stun Gun is a slim, pocket-sized case that packs a punch. The two electrodes on top transfer a pant-wetting 950,000V charge. And it will even recharge your phone if you run out of juice!

1in Armor Bulletproof Case is the heaviest, strongest iPhone case in the world. The 1.5in iron backing was designed to withstand a 50cal at point blank range. Unfortunately, it will make you phone a little more cumbersome. 

Flir One Thermal Imaging Case will add a whole other dimension to your selfies. While it may be great for troubleshooting heat leaks around the house, it is also a great way to hedge your bets in the field. Just imagine the applications in a collapse setting. Seeing through walls, or night recon.