Our Adafruit Bluefruit LE (Bluetooth Smart, Bluetooth Low Energy, Bluetooth 4.0) nRF8001 Breakout allows you to establish an easy to use wireless link between your Arduino and any compatible iOS or Android (4.3+) device. It works by simulating a UART device beneath the surface, sending ASCII data back and forth between the devices, letting you decide what data to send and what to do with it on either end of the connection.
Unlike classic Bluetooth, BLE has no big contracts to sign and no major hoops that you have to jump through to create iOS peripherals that you can legally design and distribute in the App Store, which makes it a great choice compared to classic Bluetooth which had (and still has) a lot of restrictions around it on the iOS platform.
And now that Android also officially supports Bluetooth Low Energy (as of Android 4.3), it's also -- finally! -- a universal communication channel covering the main mobile operating systems people are using today.
Please note! Adafruit still manufacture and support the nRF8001 Bluefruit module sold here, but adafruit really recommend going with the fresh new Bluefruit LE nRF51822 based modules, they're much more powerful and thus need less code on the Arduino side, have a lot more capability and flexibility so you can do more, require fewer pins, are overall smaller, can be updated with new firmware and are FCC/CE approved! They come in both UART and SPI interface type (both have same functionality, one just uses serial, one uses SPI).
The nRF8001 is nice in that it is just a BLE 'peripheral' (client) front-end, so you can use any micrcontroller with SPI to drive it. Adafruit have example C++ code for Arduino, which you can port to any other microcontroller, but some microcontroller is required - it is not a stand-alone module!
This is a product for ADVANCED USERS - At this time we recommend this product for people who are either OK with using the apps available (Nordic's UART demo or our Bluefruit LE Connect) or are comfortable with writing iOS apps (and can refer to our App repository). We do not have a tutorial for writing your own iOS or Android BLE app at this time, don't worry we're working on one :)