Apple on Friday afternoon released iOS 5.0 beta 4 to developers via the software's new over-the-air (OTA) Software Updater, marking the first time it's tested the functionality externally.



From Apple Insider:

Although developers are able to begin downloading the update over a WiFi or 3G connection with low battery life, installation of OTA updates are prohibited unless an iOS device is plugged into a power source or has at least 50% of its battery life remaining -- the installation button is simply grayed out (as can be seen below).

Friday's OTA beta is a delta update weighing just 133MB, which saves users from having to download an additional 730.8MB of redundant data that was distributed as part of the previous iPhone 4 GSM release, which weighed in at 863.8MB.

  Apple begins testing over-the-air updates with iOS 5.0 beta 4