Some things are just scary, such as snakes, meetings with the boss, muggers, and going on a first date. Douglas Adams, the author of The Hitchhiker's Guide to the Galaxy series, foretold the development of a technology that would help you avoid these dangers.
In The Restaurant at the End of the Universe, one character put on Joo Janta 200 Super-Chromatic Peril Sensitive Sunglasses. Whenever he encountered something dangerous, they darkened. If he was in dire peril, they went completely black. Thus these sunglasses ensured his safety, or at least prevented anxiety.
For a contest, Hack A Day member Minimum Effective Dose made Douglas Adams's idea a reality. He used body temperature and galvanic skin response sensors to trigger sunglasses that darken when the user is stressed.
This demonstration shows a stressful encounter with a sonic screwdriver.