Question: My bluetooth mouse batteries died, and when I replaced them, the mouse didn't reconnect. Now how can I get OS X to discover and connect my mouse without having a mouse to open the mouse dialogue?

Answer: 
You can open the Mouse System Preferences by using Spotlight search. 

1. Press `⌘-Space` to open Spotlight. Type "mouse" to find the Mouse System Preferences and press `Enter`.
2. When the Mouse Preferences are opened, make sure the mouse is on and wait for it to be discovered. The "Connect" button should be blue, so you can press `Enter` to connect to it, and you're done.
Make sure your mouse has been reset.

1. Press `⌘`+`Space` and type "Bluetooth" to open bluetooth in System Preferences. You will see your mouse in the list of devices and a button to 'Connect'.
2. Use the `Tab` key to move to the next control, this will highlight the next one for you (If you are stuck on the text field, press `Ctrl`+`Fn`+`F7` to switch between navigation of all controls on the screen, press `Ctrl`+`F7` to switch back).
3. Once nothing is highlighted in the window, press the `Space` bar, this in turn selects the 'Connect' button for you.