Like most widespread technologies, there is a standard and a standards body behind Bluetooth. In this case, it's the aptly named Bluetooth Special Interest Group (SIG). Ericsson invented Bluetooth and formed the Bluetooth SIG (http://www.bluetooth.com/) in February 2001. The Bluetooth SIG now boasts more than 2000 members, including Ericsson, Nokia, IBM, Microsoft, Intel, and, of course, Apple Computer.
Because the Bluetooth standard is designed for short-range, point-to-point data transfer between devices, no central hub (such as those used with, say, Ethernet, or a Wi-Fi access point) is needed. Like any wireless radio standard, you don't have to be within line of sight for two Bluetooth devices to communicate (though because the effective range is so short, you usually will be). Bluetooth shares the unlicensed-use 2.4 GHz band with Wi-Fi, and it is susceptible to the same sorts of household interference as Wi-Fi signals, such as microwave ovens and some cordless phones. In fact, running Bluetooth devices in the presence of Wi-Fi devices can result in some interference between the two, but it is usually not a big problem. Because Bluetooth can use a spread of many slightly different radio frequencies to transmit and receive data, it is fairly resistant to interference. If there is interference, the Bluetooth devices may simply need to resend a few data packets.
When two or more Bluetooth devices connect, they form an ad-hoc network called a piconet. A piconet can contain up to eight devices, and must contain one master (the device that initiates the connection) and one or more slaves (devices that were found by the master device). The important point here is that you can have no more than eight Bluetooth devices active and simultaneously connected. If one of those devices is your computer, and it uses Bluetooth to connect to its keyboard and mouse, you're already using three devices right there. You can quickly fill up the remaining slots with a Bluetooth-enabled cell phone, a PDA, and other devices, such as a digital camera.
Mac OS X allows you to use Bluetooth to transfer files between Bluetooth devices or synchronize information between devices. File transfers use the Bluetooth File Exchange application, found in /Applications/Utilities/ (see Section 6.3.4 later in this chapter). For synchronization, Mac OS X relies on the iSync application (more about that later in this chapter, Section 6.5).