Chapter 2: Trends Towards Mobility 19 pump music into headsets. More sophisticated players allow managing of playlists (section 2.7), and include functions beyond music use. For instance, Apple’s iPods do games, slide shows, contact lists, and even videos. The various iPod accessories have developed into a rich gadget and fashion market of their own. It could be said that the two key functions of an iPod are music enjoyment and personal expression. As a consequence, iPod has gradually transformed into a “Swiss army knife” (see below). 2.2.1.4 DVD Players DVD players were offered in portable formats fi rst for vehicle use and later for other personal use. The relatively large screen sizes (at least compared to phones and iPods) can offer suffi cient viewing quality for nomadic users, but usage while walking is not practical. It seems that dedicated video players are preferable for extended viewing, and smaller devices excel for quick video clips for those gaps in life. The UIs in dedicated players are minimal, which can be suffi cient for their intended single purpose. 2.2.1.5 Fitness Monitors This is yet another class of devices that are becoming multi-purpose gadgets. The original functions, like heartbeat monitoring or step count- ing, are being supplemented by navigation, compasses, altimeters, and other kinds of sensors. Typical mobile fi tness monitors include separate sensing devices, such as chest bands, shoe sensors, and UIs in wrist- worn units. Such devices are best for data gathering and occasional monitoring, but other functions can be cumbersome due to the small size. Figure 2-4. A mobile GPS navigator with multi-continent maps. Featuring a hard disk, this device still has extra memory space to accommodate MP3 music and digital photos.