I collect watches (don't ask).
A few companies have produced one-handed watches
from
time to time. These are normal watches, but they lack
the
minute and second hands. They're a little strange at
first,
but in fact you can read the time quite accurately,
simply
by using the hour
hand.
I think it would be cool (OK, "cool" is not the word.
"Mildly
interesting" or "possible" is probably closer) to make a
single-handed watch with a Vernier Moiré dial and a
single
(hour) hand.
The minute-markers around the periphery of the dial
would be closely spaced (in fact, one line for every 10
seconds). The single hand would have, at its end, a
small
transparent paddle marked with lines (running radially)
at
a spacing corresponding to one every 9 seconds.
As the hour hand moves, you would read the time to the
nearest 5 minute interval in the usual way (from the
position of the hand). But, as the hand moved, a Vernier
or Moiré pattern would sweep slowly across the little
paddle. From the position of this pattern on the paddle,
you'd be able to read the time down to the last minute or
better.
This would need the hour hand to be well fitted, to leave
only a small gap between the paddle and the dial,
otherwise parallax would affect your reading of the
time.
There are other possibilities, of course. For example, if
the hour hand were replaced with a transparent plastic
disc, and if suitably spaced radial lines were engraved on
the dial and the disc, you could create three concentric
Moiré patterns which behaved like the hour, minute and
second hands of a normal watch.