Magic Mouse Battery Plug In I'm new to mac and everything around, I just want to know if I can code a sort of plug-in to show the batterie of the magic mouse, in the menu bar.

What is the type of template i have to choose in Xcode to realize my idea.
The Magic Mouse battery level is shown under the device name in the Bluetooth menu. You can install an app such as iStat Menus for easier access to such information directly in the menu bar. Software development questions are off-topic here.