The BEST widget for your lockscreen. Built by a Google Employee it works well and has all the features needed for glanceable information. You get all that and there is a great developer community supporting it through the extension framework.
If you thought DashClock was extensible, this expands that notion 10-fold. If there is an app installed on your phone, you can wire up a custom extension to launch an app, or a specific activity within that app.
What's the big deal? I can already see how much charge I have. This goes beyond simple charge percentage, it can give you temperatures, charge/discharge time estimates, it is a great addition. Also it isn't spammy like the other extension.