I went creeping around the "package contents" of iSync, and sure enough, there are two picture files which make up this title-bar effect. they are...
iSync/contents/resources/ISyncSGBackground.tiff
and
iSync/contents/resources/ISyncSGSlash.tiff
if you want to do it yourself, I suppose you'd have to specifically make your app use those picture files as a title bar. See attached screen shot to see the files by themselves