– Wi-fi ‘Scan Only’ mode – When users switch off Wifi, coarse positioning ability (through geolocation providers like Skyhook) is negatively affected. ‘Scan Only’ mode allows for Wifi to periodically switch on to locate nearby networks for geolocation, then switch off again. This ties in with geofencing and the new ‘Fused Location’ provider – allowing for location through non-GPS sensors, thus saving loads of battery. For the security conscious, there is a new toggle under Wifi in Settings, to completely switch off scan mode.
– Rendering improvements – Text and shape renderer improved, renderer pipeline efficiency improved, window buffer allocation improvements. Net result, faster and sharper display of everything. Improved multithreading support, should allow for preserved user responsiveness even when individual threads are busy/locked. There are also a whole bunch of overlay API improvements. It’s possible that there may be substantial battery savings here, not to mention making older devices ‘feel’ much faster.
– Profile Security – Multi-user mode as seen in 4.2 for tablets was very useful, with each user having their own data profile. Now, moving more towards desktop style security, individual accounts can have specific access locked down. Developers can specify app actions when accounts don’t have access to locked resources, presumably for more graceful fallback. There’s also keychain improvements, including stricter key access per user and SETUID permissions are more strictly locked down.
– SELinux – SELinux is a set of kernel modifications, originally created by the one and only NSA, built on top of Linux that acts to enforce security policies (and prevent rogue apps from causing damage). It’s pretty serious stuff, I wonder to what extent it’s being used in 4.3.
– Media streaming improvements, to tie in with Chromecast, allowing for remotely-played streams to be controlled from multiple devices. There’s also AVRCP 1.3 media streaming quality improvements, and streaming of single surfaces to a single MP4 video/audio stream (potentially desktop-style streaming, think of Chrome Remote Desktop or Hangouts Remote Desktop).
– WLAN EAP Support – Enterprises love 802.1X Wifi authentication, now 4.3 loves EAP.
– OpenGL ES 3.0 support, bringing it in line with current spec. Improved texture, shading and acceleration features, should result in better looking games once developers update.
– Bluetooth low-energy, an extension to the BT 4.0 spec, allows for super-low power devices (in the microamp range). Think of fitness or health trackers that have months of battery. Many newer devices (like 4S/5, HTC One, GS3/4 already have hardware support for this).
– Notification listener, previously apps which wanted to act on your notifications (like Dashclock, Tasker or SMS forwarders) previously needed to be registered as an Accessibility helper, requiring manual user action. Now, apps can apply for notification listener permission, more streamlined.
– Other: More localisation improvements, and Master Key exploit, has of course been patched :) For developers, better systrace and GPU profiling improvements.