Anker 10k Powercore Battery Pack
Another invaluable smartphone accessory is the portable battery pack and charger. You never know when an emergency situation will emerge, and you'll need to recharge your phone or tablet.
Anker makes some of the best portable battery packs on the market. This holds 10,000 mAh of battery, which will likely recharge any phone you own three times. I have one of these in my glove box 24/7 just in case. It won't make using your phone easier in the car, but you'll be glad you had one when you really need it.