Most smartphones come standard with an accelerometer, but only a few also include a gyroscope. Accelerometers help keep track of the position your phone is in; if you turn it onto its side, the display switches from portrait orientation to landscape mode. Accelerometers are also used in certain applications. In driving game apps, for example, the accelerometer lets you steer your car by tilting your phone from side to side.
Gyroscopes permit more-accurate recognition of movement in a 3D space. If you move your phone away from or toward yourself, the gyroscope can detect that motion. The feature is chiefly useful for gamers, as it makes precise motion-based gaming controls possible. In the future, the gyroscope may play a central role in controlling new and different types of apps. But for now, nongamers are likely to be content without this piece of hardware.
Bluetooth and Wi-Fi
Both Bluetooth and Wi-Fi have become common features on smartphones in recent years.
Bluetooth is a wireless technology that enables you to transfer and receive data between two devices at relatively short range--similar to the way two-way radios work. You can use Bluetooth to transfer files between a phone and an accessory such as a headset, or between a phone and a PC--for example, to transfer photos between your phone and your laptop for editing and viewing.
You're likely to see two flavors of Bluetooth in the marketplace today: Bluetooth 2.1 and Bluetooth 3.0. The practical differences between versions 2.1 and 3.0 involve range and data speed. Bluetooth 2.1 supports very short-range (around 33 feet maximum) radio communication between two mobile devices. Though not ideal for transferring files, it is adequate for creating a wireless link between a phone and a Bluetooth headphone or headset.
Bluetooth 3.0 works across a much wider range and can transfer large files quickly (at a rate of around 24 mbps) via an 802.11 link. Since Bluetooth 3.0 is still relatively new, not all phones and accessories can take advantage of the speed and range that 3.0 offers.