Automatic App updates in iOS 7
iOS 7 has a feature that allows iPhone and iPad to automatic download app updates. Currently you would have noticed on your device that the App Store showing the number of available app updates as notification. In the below screenshots, there are 5 app updates available and launching App Store will display the Available Updates. Now you can manually install these updates by tapping Update All (for all apps) or UPDATE (individual app) button.
And in IOS 7, you can enable the automatic updates app using the option available as part App Store settings
Step 1: Tap the Settings icon on Home screen.
Step 2: Scroll down the Settings screen and tap iTunes & App Store.
Step 3: In the iTines & App Store settings, scroll down to AUTOMATIC DOWNLOADS section and turn on the switch for Updates.
This should enable the automatic downloads of App updates for your device. The notification section should display the app updated message as shown in below screenshot.
If you want the device to download app updates only on WI-Fi connection and not in 3G or 4G connection. Then make sure turn off the Use Cellular Data option.