Introduced in the summer of 2013 as a feature of iOS 7, Apple's new mobile notifications system iBeacon is being touted by big brands as the next great opportunity in advertising. Using tiny Bluetooth wireless transmitters affixed to buildings, iBeacon lets companies send iPhone owners specific pop-up notifications based on their location and proximity to stores and products. But privacy advocates are concerned it could also be too invasive. Follow the spread of iBeacon as more organizations adopt it in an effort to sway customers through their most personal of devices.