the hitchhikers guide to the galaxy - Where did the idea of the POV gun come from?

Where did the idea or concept of the Point of View gun originate in the Hitchhiker's Guide to the Galaxy film?

I've checked the books, and couldn't find it.

Answer

In 2005, Slashdot conducted an interview with Robbie Stamp, executive producer of the movie, where he answers this question:

All the substantive new ideas in the movie, Humma, the Point of View Gun and the "paddle slapping sequence" on Vogsphere are brand new Douglas [Adams] ideas written especially for the movie by him.

Although I can't say for sure where he got the idea, the POV gun was a bona fide Douglas Adams invention.

As I mention in a comment to Joe L's answer, the POV gun has some non-trivial similarities to the Total Perspective Vortex. From Chapter 11 of The Restaurant at the End of the Universe:

The man who invented the Total Perspective Vortex did so basically in order to annoy his wife.

Trin Tragula — for that was his name — was a dreamer, a thinker, a speculative philosopher or, as his wife would have it, an idiot. And she would nag him incessantly about the utterly inordinate amount of time he spent staring out into space, or mulling over the mechanics of safety pins, or doing spectrographic analyses of pieces of fairy cake.

"Have some sense of proportion!" she would say, sometimes as often as thirty-eight times in a single day.

And so he built the Total Perspective Vortex — just to show her.

This is just speculation, but it's possible that Adams thought the idea of a person inventing a reality-warping device just to spite their nagging spouse was too good of a joke to pass up. Hence, he re-worked it into the POV gun.