iBeacon is the Apple Trademark for an indoor positioning system that Apple Inc. calls "a new class of low-powered, low-cost transmitters that can notify nearby iOS 7 devices of their presence." They can also be used by the Android operating system (limited to central-only). The technology enables an iOS device or other hardware to send push notifications to iOS devices in close proximity.
The iBeacon works on Bluetooth Low Energy (BLE), also known as Bluetooth Smart. BLE can also be found on Bluetooth 4.0 devices that support dual mode. One potential application is a location-aware, context-aware, pervasive small wireless sensor beacon that could pinpoint users' location in a store: iBeacons could send notifications of items nearby that are on sale or items customers may be looking for, and it could enable payments at the point of sale (POS) where customers don’t need to remove their wallets or cards to make payments. It could be a possible Near Field Communication (NFC) competitor.
It uses Bluetooth low energy Proximity sensing to transmit a Universally unique identifier picked up by a compatible app or operating system that can be turned into a physical location or trigger an action on the device such as a Check-in on social media.
The beacons come in different formats, including small coin cell powered devices, USB sticks and software versions.
Region monitoring is limited to 20 regions and can function in the background (of the listening device) and has different delegates to notify listening app (and user) of entry/exit in the region - even if app is in the background or phone is locked.
Ranging works only in the foreground but will return (to the listening device) an array (unlimited) of all iBeacons found along with their properties (UUID, etc.) 
An iOS device receiving an iBeacon transmission can approximate the distance from the iBeacon. The distance (between transmitting iBeacon and receiving device) is categorised into 3 distinct ranges:
- Immediate: Within a few centimetres
- Near: Within a couple of metres
- Far: Greater than 10 metres away
An iBeacon broadcast has the ability to approximate when a user has entered, exited, or lingered in region. Depending on a customer's proximity to a beacon, they are able to receive different levels of interaction at each of these 3 ranges. The maximum range of an iBeacon transmission will depend on the location and placement, obstructions in the environment and where the device is being stored (e.g. in a leather handbag or with a thick case).
||This section possibly contains unsourced predictions, speculative material, or accounts of events that might not occur. (December 2013)|
In mid 2013 Apple introduced iBeacons and experts wrote about how it is designed to help the retail industry by simplifying payments and enabling on-site offers. With the launch of iOS 7, retailers and other small to medium enterprises will be able to use this Bluetooth 4.0 based technology. On December 6, 2013, it was reported that Apple activated iBeacons across its 254 US retail stores.
- iOS devices with Bluetooth 4.0 (iPhone 4S and later, iPad (3rd generation) and later, iPad Mini (1st generation) and later, iPod Touch (5th generation).
- Android devices with Bluetooth 4.0 and Android 4.3 and later (Samsung Galaxy S3/S4/S4 Mini, Samsung Galaxy Note 2/3, HTC One, Google/LG Nexus 7 (2013 version)/Nexus 4/Nexus 5, HTC Butterfly (aka Droid DNA).
- Macintosh computers with OS X Mavericks (10.9) and Bluetooth 4.0
- Passkit GemTot Proximity Beacons with Apple Licensed iBeacon Technology 
Although the NFC environment is very different and has many non-overlapping applications, it is still compared with iBeacons.
- NFC range is up to 20 cm (7.87 inches) but the optimal range is < 4 cm (1.57 inches). iBeacons have a significantly larger range.
- NFC can be either passive or active. When using passive mode, the power is sent from the reader device. Whereas although Passif (bought by Apple Inc.) has worked on reducing the energy consumption, a battery pack is still needed inside iBeacon tags at this time.
- Most smartphones ship with both Bluetooth 4.0 LE and NFC support but at this time, no iOS devices have been released with NFC support.
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