NASA's Apollo spacecraft had briefcase-size computers that for their day would normally have filled two rooms. Apollo Instruments has been able to shrink the Apollo Guidance Computer even more.

You can now wear an Apollo Guidance Computer keypad as a wristwatch

Source: space
Source Link: https://www.space.com/space-exploration/apollo/you-can-now-wear-an-apollo-guidance-computer-keypad-as-a-wristwatch