After having updated my MacBook Pro to Mountain Lion, I really miss the feature where I can see the battery time remaining in the menu bar!
Recently I discovered the “Battery-Time-Remaining” project on GitHub, which enables you to show the battery time remaining in the menu bar. The setup is very easy:
1) Download the app from https://github.com/codler/Battery-Time-Remaining
2) Drag the app to the Applications folder.
3) Run the app
4) Go to System Preferences -> Energy Saver and uncheck “Show battery status in menu bar” (unless you want two battery icons in your menu bar)