What is bluetooth?

Bluetooth is sort of a competitor to wifi, but it's designed to only have a range of a few feet: if you're not darn close to a bluetooth device you shouldn't be able to see it or interact with it.

Fortunately Wikipedia has a splendid definition in its article on Bluetooth. Here are a few of the most important passages:

"Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices like personal digital assistants (PDAs), mobile phones, laptops, PCs, printers and digital cameras via a secure, low-cost, globally available short range radio frequency."

"Bluetooth lets these devices talk to each other when they come in range, even if they are not in the same room, as long as they are within up to 100 metres (328 feet) of each other, dependent on the power class of the product. Products are available in one of three power classes."

"Pairs of devices may establish a trusted relationship by learning (by user input) a shared secret known as a "passkey". A device that wants to communicate only with a trusted device can cryptographically authenticate the identity of the other device. Trusted devices may also encrypt the data that they exchange over the air so that no one can listen in. The encryption can however be turned off and passkeys are stored on the device's file system and not the Bluetooth chip itself. Since the Bluetooth address is permanent a pairing will be preserved even if the Bluetooth name is changed. Pairs can be deleted at any time by either device. Devices will generally require pairing or will prompt the owner before it allows a remote device to use any or most of its services."

"One of the ways Bluetooth technology may become useful is in Voice over IP (VOIP). When Voice over IP becomes more widespread, companies may find it unnecessary to employ telephones physically similar to today's analogue telephone hardware. Bluetooth may then end up being used for communication between a cordless phone and a computer listening for Voice over IP and with an infrared Peripheral Component Interconnect (PCI) card acting as a base for the cordless phone. The cordless phone would then just require a cradle for charging. Bluetooth would naturally be used to allow the cordless phone to remain operational for a reasonably long period."

And, the most interesting snippet of all:

"The system is named after a Danish king Harald Blåtand (Harold Bluetooth in English), King of Denmark and Norway from 935 and 936 respectively, to 940 known for his unification of previously warring tribes from Denmark (including Skåne, present-day Sweden, where the Bluetooth technology was invented) and Norway. Bluetooth likewise was intended to unify different technologies like computers and mobile phones. The Bluetooth logo merges the Nordic runes analogous to the modern Latin H and B: ? and ?. This is the official story; however, the actual Harald Blåtand that was referred to in naming Bluetooth was most probably the liberal interpretation given to him in The Long Ships by Frans Gunnar Bengtsson, a Swedish best-selling Viking-inspired novel."

So now you know more about bluetooth than you probably wanted to learn, but it's a very interesting low-range networking system that powers a lot of otherwise wireless devices.