Dear Peter

For Hindi, Kira Hall's work is probably a good place to look. See, e.g.,

Hall, Kira. “Exceptional Speakers: Contested and Problematized Gender Identities.” In Handbook of Language and Gender, edited by Miriam Meyerhoff and Janet Holmes, 352-80. Malden: Blackwell, 2003.

Hall, Kira, and Veronica O’Donovan. "Shifting Gender Positions Among Hindi-speaking Hijras". In Victoria Bergvall, Janet Bing, and Alice Freed (eds.), Rethinking Language and Gender Research: Theory and Practice. London: Longman, 1996, 228-266.

or her other works - many downloadable from her website: http://www.colorado.edu/linguistics/faculty/kira_hall/publications.htm

Gayatri Reddy has written on hijras in Andhra, but I don't recall what (if anything) she says about language.

Reddy, Gayatri. With Respect to Sex: Negotiating Hijra Identity in South India. Chicago: University of Chicago Press, 2004.

Best wishes

Will