Often, for some precision tasks such as graphic design, computer-aided design and modeling, and editing large and complex documents, it's more convenient to use a mouse along with the laptop rather than the trackpad. Apple believes that carrying a separate mouse can become cumbersome, so they've come up with a way to build a mouse right into the MacBook keyboard.
How does it work?
The idea is described in a patent application that was filed with the US Patent and Trademark Office . The documentation refers to a regular MacBook keyboard with a scissor system. Only in it hides a removable key that also acts as a mouse.
The illustrations of the patent show a retractable key closer to the edge of the keyboard, so it will not be used often. By design, the key has a small battery. The keyboard uses it as a regular key, and when removed - it turns into a mouse. It will have a position sensor in which will allow you to control the cursor on the screen.
Of course, there are doubts that such a mouse will be comfortable to use as it is too small. But we should not forget that this is only a patent, so will not be surprising if the idea remains on paper.