Stopwatch that can be syncronized across a network of computers?

"You haven't specified the operating system.

I don't know of any prepackaged solution. I'm thinking about two possibilities:

Solution 1

VNC protocol using single-window mode: On the master computer set up and start a VNC server supporting single-window mode and launch any stopwatch application. To display the time on other computers use a VNC client and connect it to the VNC server/remote window.

Solution 2

If you can work on a terminal it can be done with a stopwatch/counter and netcat to pass the result (e.g. elapsed time) to other computers.

Example:

Stopwatch example using a command-line stopwatch from here and a netcat for windows binary from here:

Batch file on the master computer (it should be on the same directory as stopwatch.exe and nc.exe).

@echo off
stopwatch start > timestamp.txt
pause > null
stopwatch stop < timestamp.txt > elapsed.txt
nc -d -w 1 remote-pc-1 4444 < elapsed.txt
nc -d -w 1 remote-pc-2 4444 < elapsed.txt
...
type elapsed.txt

(replace remote-pc-N appropriately, press any key to stop counting)

On the remote computers:

nc -L -p 4444

Also replace port 4444 if used."

"You might try this program (haven't tested it myself though):
http://download.cnet.com/MultiTrack-Stopwatch/3000-2350_4-10122220.html"