The Hitchhiker's Guide to the Galaxy has a few things to say on the
subject of towels.

A towel, it says, is about the most massively useful thing an
interstellar hitchhiker can have.  Partly it has great practical
value.  You can wrap it around you for warmth as you bound across the
cold moons of Jaglan Beta; you can lie on it on the brilliant
marble-sanded beaches of Santraginus V, inhaling the heady sea vapors;
you can sleep under it beneath the stars which shine so redly on the
desert world of Kakrafoon; use it to sail a miniraft down down the
slow heavy River Moth; wet it for use in hand-to-hand combat; wrap it
round your head to ward off noxious fumes or avoid the gaze of the
Ravenous Bugblatter Beast of Traal (a mind-bogglingly stupid animal,
it assumes that if you can't see it, it can't see you - daft as a
brush, but very very ravenous); you can wave your towel in emergencies
as a distress signal, and of course dry yourself off with it if it
still seems to be clean enough.

        [ The Hitchhiker's Guide to the Galaxy,
          by Douglas Adams ]

Towel is aimed to prevent repetitive strain injury (RSI). It monitors
the X input events and if the operation time exceeds the limit, a
window is popuped occupying the whole screen, preventing further
operations thus users are forced to take a break.