Sorry to break it to you, Oscarr, but I can generally tell.
My point - possibly not obvious to someone who hasn't laboured at it for hours - is that the unnaturalness of speaking very slowly may well produce some of the other aspects you mention; particularly the monotony and stretched vowels. It's hard to speak very slowly and still maintain natural variation in vocal patterns, and I find mine tend to flatten. I'm not so sure about the emphasis rhythm.
There are definitely particular inflections and rhythms which have common patterns ("in the name of the Father, and of the Son, and of the Holy Spirit" is a phrase which strikes me as having a common received pattern of inflection, for example). And possibly also particular patterns of emphasis to cue congregational responses. Beyond that I'm not sure, and it would be easier for me to comment if you could post an example or two?