The XP1-Power is a little bulkier than your average USB cable, but it has good reason: it packs a back-up battery in-line. XMultiple have improved on their older version, now boasting 20 hours of extra juice and surge protection.
https://gizmodo.com/x-power-1-iphone-usb-cord-comes-with-built-in-rechargab-5325035
In addition to the surge protection, the XP1 is now compatible with several adapters that allow for the charging (and back-up juicing) of a variety of smartphones, MP3 players, GPS devices and the like. The adapters come at $4.99 a pop and the cable itself is $49.99. [XMultiple]
