The first commercially successful embedded Linux device is TiVo, which lets you digitally record television programs and play them back whenever you want.
TiVo works like this: Late at night, it uses its built-in modem to call a central TiVo server, which contains all of the programming information for the next few days. You are then able to tell TiVo which program(s) you want to record. It records the program(s) and stores the data on a built-in hard drive, and you can then play back the recorded show(s) whenever you want.
TiVo also allows you to “pause” live television. That is, you can press a key on your remote, and the current program will begin recording. You can then press the play button to begin watching the recorded show. Similarly, you can “rewind” live TV. The TiVo is always recording the last 30 minutes of whatever you’re watching, so you can always rewind whatever you’re watching… neat.
While the TiVo is an embedded Linux device, it doesn’t suffer from the space restraints of many other embedded devices. There’s a lot of room for software on the hard drive, where the recording software itself resides. Even so, the TiVo designers chose some interesting hardware. Much of the following information came from the TiVo FAQ (http://www.tivofaq.com/hack/faq.html).