Simply put, an iBeacon is a Bluetooth low energy (BLE) device that emits a signal that conforms to the iBeacon specification. The iOS 7 SDK includes updates to the Core Location and Core Bluetooth frameworks that will allow you to build apps that respond to iBeacon signals or even act as an iBeacon transmitter.
The iBeacon specification for building hardware beacons is only available under nondisclosure agreement to vendors who sign up to the Made for iPhone (MFi) program. However, as an iOS developer, you don't need to know how to build hardware, you only need to understand how to interact with iBeacons or to simulate them with an iOS device, all of which we will cover in this book.
BLE is a groundbreaking leap in classic Bluetooth technology that allows the development of devices that can broadcast a signal up to 100 m (330 ft) with very little power consumption. This means that beacons can be produced for as little as $ 5 and broadcast for up to 2 years on a single lithium watch battery.