Prosody is defined as "the study of rhythmic structure, intonation, stress, and related attributes in conjunction with syntax in speech and signing".
In sign language, prosodic features include: duration of a sign, pause, eye aperture, facial expression, use of signing space, etc.[a demo in video coming soon]
A sociolinguistic researcher studied in search of sociolinguistic factors as to why Deaf people sign with a pinky extension and to determine whether it is a variation. An interesting finding was that:
"pinky extension tended to co-occur with prosodic features of emphatic stress. Specifically, it tended to occur (a) with lexemes used repeatedly within a discourse topic, (b) before pauses, and (c) with lexemes lengthened to almost twice their usual duration. This suggests that pinky extension is itself a prosodic feature of ASL that adds emphatic stress..." -- Linguistics of ASL (2005), p 465.
Dachkovsky, Svetlana; Sandler, Wendy. "Visual Inonation in the Prosody of a Sign Language." Language and Speech, 2009. Pp 287- http://sandlersignlab.haifa.ac.il/pdf/Visua_Intonation.pdf
Nicodemus, Brenda. "Prosodic Markers and Utterance Boundaries in American Sign Language." Gallaudet University Press. http://gupress.gallaudet.edu/excerpts/PMUB.html
Sandler, Wendy. "Prosody and Syntax in Sign Languages". 2010. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250094/
Related topics: emphatic stress in sign language.