I came a cross this app when checking for a way to see how well my vintage watches kept time.

App website: http://www.coldflower.com/twixt/
the App is about $5 (I only see my local currency in the AppStore)

it works by way that you take a picture of the watch and mark out 12" and the hour,minute and second hands. You repeate the same procedure 24 hours later and the App calculates the time difference.

It can be a bit trickey mark the 12" marker correct resulting in a false reading. It worked perfect on my vintage Tissot but had some problems with my Seamaster De Ville.

This how you do it:

Marking out center of the dial


Marking out 12"


Marking out hour hand

The app calculates the time and you repeat the same procedure 24 hours later

You can create profiles for different watches

 

Yes that would be interesting to know.

 

Reminds me of the clever "clock code" on the last season of The Wire

You could casually check the apps accuracy by simultaneously checking your watches by http://tycho.usno.navy.mil/what.html

 

Accuracy, schmackurassee. If you own multiple watches, it isn't that important. Guess it's a cool toy though.

 

I get that , however if you sell one of your watches , the questions is often raised by the buyer

 

I guess it would require the watch to be sitting in the same position and in the same temperature as the timing machine before it will give a similar reading?
The clocks of computers in general (and the iPhone is but a small clever computer) are not very accurate either.
Using automatic time synch services fixes this on a "connected computer", but I have experience from stand alone computers that actually drifts more in time than some of my mechanical watches would have.
Now give me an app that uses the iPhone microphone, and the software of a timing machine, and I would line up to pay much more than 5 USD!

 

Now that would be brilliant!

 

There's such an app, but I found it *very* difficult to use and I'm not sure it's so accurate. https://itunes.apple.com/us/app/kello/id380539253

When I tested this on a late 60s Genève which is my daily beater it said it was gaining 0.02s/d. I mean, as cute as the little watch might be it's not even chronometre grade or anything.