Apple's AirDrop could eventually encrypt data before sending it to another device, which can be used for backup. The company has filed for a patent (number 20150230078) with the U.S. Patent & Trademark Office for "secure ad hoc data backup to nearby friend devices."
AirDrop helps you quickly transfer files between your Mac and nearby Mac computers or iOS devices using Wi-Fi. You don't have to be connected to the same network in order to transfer files – your devices automatically set up a direct wireless connection for AirDrop.
AirDrop is available from the Finder, the Share menu, and in Open and Save windows. When you choose AirDrop in Yosemite, your Mac looks for nearby devices that can also use AirDrop. This includes Macs with OS X Lion or later installed, and iPhone, iPad, and iPod touch devices with iOS 7 or later.
According to Apple's patent filing, when the user of an iOS device has poor or no data connectivity with a network-based storage system and friends are identified that are in the vicinity of the user, backup data is transferred from the user's mobile device to one or more of the friend devices using peer-to-peer connections.
What's the purpose of the invention? Apple says that, "In many situations, the user of a mobile device in the ad hoc network may be collecting data (e.g., photos, notes) at a time where there is no connectivity with a data backup server. If the mobile device is damaged, lost or stolen during this period of no connectivity, the data may be lost."