VPN on the iPhone or iPod touch

most apps on the iPhone or iPod touch don't have individual preferences screens as they do in OS X or in Windows. Instead, you'll access these options from the Settings app. This is also where you can change system-wide settings, such as sounds and choice of wallpaper. Here you'll also find a toggle for Airplane Mode (which disables cellular antennas for safe usage on an airline) and networking options.Because this app does so much, it's by far the most crowded space on your device—there are fourteen separate menus on the main screen, plus entries for any third-party apps (see "One Menu to Rule Them All"). It can get pretty confusing, pretty fast—so let's slow down and take a quick look at each of the main preferences.Airplane modeIf you travel frequently, Airplane Mode is a necessity: it temporarily switches off the cellular antenna—and other potentially unfriendly  that could interfere with the airplane's navigational system, allowing you to safely use the device in the air once the captain gives the all-clear.When Airplane Mode is on, an airplane will replace the bars in the upper left corner of your screen, and all Phone settings will be grayed out. Thankfully, the phone still allows Wi-Fi connections, so if you happen to be taking a flight on one of the airlines that currently supplies Wi-Fi access, you'll be able to surf the Web and Twitter away.