If you've always wanted to shoot time-lapse videos or set up a security camera, TriggerTrap is a combination mobile app and physical dongle that could be the ideal solution. It lets you manage your phone's settings, start recordings, and take pictures remotely from your iOS or Android device.
In order to use TriggerTrap, you'll have to check on the dongle selection page to see if your camera is one of the 300 supported models. You can pick up a dongle for between $US10 and $US25, which pairs with a wired controller you can also buy. If you want to use your smartphone to control your camera, you can pick up the Android app at Google Play for $5 or the iOS app in the iTunes App Store for $5.49.
The mobile apps allow you to trigger recordings or photos based on decibel level in the room (ideal for security cameras), time-lapse videos either for distance (taking fewer photos over longer periods) or speed (for star-trials and sky shots), and long-exposure shots in normal or HDR modes. All of the settings are as customisable as they would be if you were holding your camera in your hands. You have to drop some coin to get set up, but you get a fast and painless way to use your phone as a remote control for your camera.
If your phone isn't supported by TriggerTrap, check out our guide to remote controling your digital camera for more solutions.