Both the LG G Watch and Samsung Gear Live are receiving pre-release over-the-air (OTA) updates today, jumping them up to build KMV78V of Android Wear (4.4W). At this time, we have no idea what is new, since nothing is standing out. Until we hear from others who received the update (assuming you went to Google I/O), we will guess that this is a bug fixer meant to polish things up a bit before those first Google Play orders of either watch arrive.
If you happen to own either watch, you can check for the update by tapping the screen, then scrolling down to Settings>About>System updates.