The Black Watch is an electronic wristwatch launched in September 1975 by Sinclair Radionics. It cost £24.95 ready-built, but was also available for £17.95, as a kit.

The Black Watch is equipped with a red LED

LEd

LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

 display, which is illuminated only when the watchcase's surface is pressed; two resilient spots display hours and minutes or minutes and seconds, respectively.

The product was beset by technical problems including low battery life, variable accuracy and a very sensitive integrated circuit

Integrated circuit

An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

which could be rendered useless by a static shock from a nylon shirt. In spite of this, Sinclair's advertising still claimed:

If that sounds technical, think of the outcome: a watch with no moving parts, a watch with nothing to go wrong, a watch which gives accuracy never achievable by the most precise mechanical engineering.