I travel a lot, and depend on my iOS devices during those travels. That makes a reliable extra battery pack an extremely important part of my travel gear. Recently I've been using a UNU battery case ($99.95), but that's specifically for my iPhone 5s. It doesn't have a USB port to power my iPad Air, and when the next iPhone comes out, it won't be compatible.
Fortunately, UNU has not one, but two external battery packs ($59.99-99.99)that offer plenty of power on the go. The Ultrapak Tour Portable Battery Pack offers what UNU calls "Ultra-X Fast Charging Technology." This sounds like something out of a superhero movie, but it's quite real. UNU is doing something revolutionary that no other battery pack I've seen does. Instead of charging the pack using USB, they charge it with the included A/C power plug. This enables them to charge the pack itself up to eight times faster than USB charged packs. They claim it only takes 15 minutes to charge the 2-USB-port model to 2,000 mAh (more than an iPhone's full charge) and 95 minutes for a full charge of a whopping 10,000 mAh. Perhaps the best part is the LCD screen that tells you how much power you have left. Too many chargers require memorizing colors or light patterns to know if you have power so this is appreciated.
This is great, because a quick stop at Starbucks would enable enough power to charge an iPhone for an entire day. You just have to remember to bring the A/C "Wall Wart" with you... but that's a small price to pay. Speaking of small prices to pay, the Ultrapak chargers are on sale now for just under $60 to $100 for the higher end model with two USB ports. There's even a flashlight, since the gadget has so much power to spare!