I saw this for Android http://forums.watchuseek.com/f11/rel...es-822115.html
and I have seen a similar app which runs on Apple phones.
It uses the microphone to listen for the ticking of a watch or mechanical clock and compares it to its own more accurate internal clock. By accurately timing the ticks it can tell if there is variation between positions and if the watch is running fast or slow even with a sample as short as a few seconds.
I imagine it would only take a few dozen lines of code to create such an app with graphing but I dont have the space on my netbook to install scratchbox. One issue is getting accurate time without background processes bogging the measurement of time or sound inputs.
It would be a cool app for watch regulating/repair geeks or before buying a used mechanical watch.

If this was 30 years ago I would have happily paid money for such an app for my N900.
Having served an apprenticeship in watchmaking and ran my own business in early to mid 1980's, I can honestly say that the machines that are needed to do this can easily run into costing thousands of pounds.

Still, it would be nice to see if this could be achieved on the N900. The basics are already there with the VUMeter app and Batterygraph.

Another mechanical time enthusiast!
I have my N900 set up with alarmd to play the ting tang chime pattern quarterly & strike the hours. I love my N900.

Quick reply...
I have a mechanical wrist watch myself. However, it ticks so quietly that VU meter doesn't seems to be able to separate it from the background noise: birds, automobiles, keyboards...
If you can get VU meter to hear only the watch, as it ticks, then you can write down a threshold command which would be performed during each tick. Something like logging precise - in milliseconds - time for each tick.
Best wishes.
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Per aspera ad astra...

My experience at home is using Biburo(free) for windows http://tokeiyade.michikusa.jp/download/
with wine on Ubuntu Linux. I needed to use a cheap 9v battery guitar preamp and piezo disc from a broken toy as mic to regulate my dive watch.
I have built a few of these watches as gifts and I can get it to within 1-4sec fast after they have been worn in for at least two months. The miyota is a pain to regulate as it just has a swing bar not a screw, having a regulating machine of some sort makes nudging it into position easier than bumping back and forth over a period of a few days.
I have heard that some people solder a clip to the piezo disc mic and can get a good takeoff by clipping to the stem(unscrewed crown?) though this would probably require taking out the case clamps and removing the movement. My old pocket watch and stopwatches would probably work with the Nokia hands free mic though.
Even so a regulating app, even if it requires a cheap preamp, would be nice even to be sure that the (forget tech term here) outer hairspring center adjust is correct if at an antique show.

Then thinking about putting the audio theough a time calibrated wave scope puts me in mind of making a ECG(heart electricity waveform monitor) that converts the output to sound readable by the phone app, or an oscilloscope for goofing with radios, though I dont think the sample rate is high enough.