Mac: You can find battery life for your wireless accessories buried in System Preferences, but there's a quicker and easier way to see how much juice they have left. Battery Status is an app that stuffs that info right in your menu bar.
You can set up Battery Status to show the battery life of your MacBook or any of your Apple accessories in the menu bar. When you click the icon, you'll get an estimate on how much time you have left in your devices and detailed info about your internal battery. If you've ever had your devices run out of juice in the middle of the day, Battery Status is a useful utility to have. It's available for $1.99 in the Mac App Store.