Thank you, all, for suggestions.

Wouter and Nate, thanks for that vacuum cleaner idea. Actually I do this for
a friend of mine that occasionally needs this work to be done.
I certainly will recommend him to try this.

As for the problem it was initially stated (to find the end of a fish tape
in the wall), a simple magnet and a compass solution suggested by Pete might
be what I was looking for.

Carl Denk wrote:
>If you have the money to buy, rent or hire with equipment, there are in
>the plumbing industry in particular fiber optic snakes that are used for
>internal pipe inspection. For a mini sized one see:
>http://www.ridgid.com/Tools/Underground-Technologies/EN/index.htm
>Roto-Rooter type people usually have one.

There are no prices there, but I can guess these are far more expensive my
friend is willing to invest.
Besides, while camera can help to understand the origin of the problem, it
will hardly help to determine the exact position in the wall.

Arkady

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