The June 2009 edition of the journal Contraception features a study called Duet® for menstrual protection: a feasibility study in Zimbabwe - you can only view the abstract here, but it gives the basic idea.
As I understand it, in an effort to increase acceptability of diaphragms, such as the Duet, as a form of contraception and STI prevention for women in developing countries, where women are disproportionately infected with HIV, it's use as a menstrual cup is being explored.
It seems the reason behind this big push to introduce (or re-introduce as is the case in India) the diaphragm is related to an increased awareness of the cervix as a vulnerable site for transmission of STIs and HIV and the need for female controlled protection.
Thanks to jordanhollya </span>for posting this link back in April which got me interested in this topic. :)