We have seen other cool mechanical gadgets that manage to interface to Google Earth before, but this is a more off the shelf solution.
By using a Wii Balance Board's Bluetooth connection and some interface software, you can use the Balance Board to act as a mouse.
Of course, you could use it to move the cursor around, but where is the fun in that? (Besides, you have no handy buttons to click, and re-mapping one of the four weight sensing domains to a mouse button would take away some of the functionality of the board.)
A better use of a Balance Board Mouse would be to go virtual surfing across the world, and with the mouse board and Google Earth you can do exactly that. Check out the video for the fun.