http://www.iphonetricks.org/remaining-iphone-battery-life-displayed-on-apple-watch/
Note: Apple has added a "batteries" widget in iOS 9 that shows both the iPhone and Apple watch battery statuses.
Yep, I have the last one on that list, Remote Battery, which is one of my primary Glances I use. prior to the 1.0.1 update it was a bit of a hassle, but that was true across all 3rd party Glances. It is much smoother now and almost always loads quickly for me, though on occasion it acts up and takes a bit to load. This is also one of a handful of apps I leave Background App Refresh on for.
Also- and my vote was for Weather for favorite complication- I leave BAR on for Weather on my iPhone as well and generally feel I have quite up-to-date and accurate weather displayed on my Watch at any given time. I actually just turned it off earlier today to see what effects it may have been having on cellular data usage due to my total usage this period apparently being through the roof (tho I am thinking there may be issues with AT&T's monitor rather than my actual consumption blasting off all of a sudden), so I'll see if I notice a lag in my weather complication.
Last point- I use the Modular Watch Face, so I have the Weather as the large center complication, which is really awesome. rather than just seeing current temp, you get your location, current temp, current conditions, and the High and Low daily temps. I really friggen love having that available with the flick of my wrist.