In my testing of MoDet I found that having the screen properly in focus is important to getting the 120ms times in Jonnythe's program. I had my camera about 12 inches from the screen which needed the macro mode on my s3. But in setting manual-focus, the camera automatically takes you out of macro-mode making things out of focus.
So I set macro-mode and not MF and all was well. The "barely see white oval on LCD before shot" effect was there along with ~120ms shot times.

THANKS ALL! EXCELLENT WORK
~~~~For those catching up to Motion Detection~~~~
Current best scripts are MD Lightning6 and 7 by Barney Fife (
http://chdk.setepontos.com/index.php/topic,405.msg3275.html#msg3275 ---with optional modifier by A570is (
http://chdk.setepontos.com/index.php/topic,405.msg3291.html#msg3291)
Get jonnythe's testing program here (
http://chdk.setepontos.com/index.php/topic,405.msg3174.html#msg3174)
Script settings mostly work as default (settings also seen in the first 19 rows of the script) only
need to adjust 'Trigger Delay' in 0.1ms increments to prevent continuous shooting. (Though you may need other adjustments for best response time.)
Works in all P, Tv, Av, M modes. MF and/or Macro only needed to ensure the subject (and not the background) is in focus.
Once you get it set properly, your camera will likely take two images per test cycle in jonnythe's program. The appropriate flash-then-shoot image and a the-line-is-still-moving-across-the-right-side-of-the-screen image. An example of a proper ~120ms image is shown in the first picture attached (6 black lines from the left edge of the screen = 120ms @20ms/line). When running properly, an image similar to the black one below shall be taken every other shot for the duration the script runs.
The second image is a test of throwing a water bottle across the field of view a la mx3's toy test:
http://chdk.setepontos.com/index.php/topic,405.msg3019.html#msg3019See! It works! Good luck!

Hope this clarifies things for people new to the thread.