The beacon market is going in various directions with regard to format and limitations, but the nRF51822 can support all the various BLE based beacons as it’s just a specific type of non-connectable BLE advertising. The difference is that the content of the advertising package may differ between various beacon implementations. The structure of the beacon package is described well in the spec description from AltBeacon (http://altbeacon.org/) and this figure.
You can with the nRF51822 be compatible with different beacon implementations by changing the content of the advertising package. There’s also an option to use the nRF51822 with the “timeslot API” in the softdevice S110 that will enable you to advertise for two different beacon configurations concurrently.
Due to changes in behavior in iOS8 compared to previous version (the Nordic vendor id is now masked out from the core location framework), there has been questions on how to make the beacon code examples and beacon kit from Nordic to act as Apple iBeacon. Nordic provides code examples for beacon functionality for various boards and configurations. These are by default setup with Nordic specific structure and may not be compliant with beacon listening devices and this specifically applies for Apples iBeacon implementation. To design an iBeacon with Nordic solution you must be an iBeacon Licensee to get the information needed to make the beacon code from Nordic iBeacon compliant.
For more information, please visit: https://developer.apple.com/ibeacon/
Nordic currently have beacon example code in the nRF51 SDK and for the nRF51822 Bluetooth Smart Beacon kit.