I still like my simple and easy audible beeper hooked up to the
enlarger light foot switch (sure helps during dodging and burning,
and I find that I sometimes change my mind on the exposure time
during the exposure, which is easy if you are just counting time
along with the beeper). It consists of one Radio Shack piezo 2 cps
beeper (with one of the two large electrolytic caps inside doubled
in size to provide 1 cps beeps), and a cheap voltage supply wired
in parallel with the switch. Works great, and doesn't tie me to
preselected exposure time intervals.
Hope This Helps