Edah recently teamed up with Ne'emane Torah va'Avodah for a series of mini-conferences on issues of concern to the Modern Orthodox community. I wasn't able to attend any of these, but according to Chakira, one session centered on the attitude of Jewish Law to Non-Jews. Predictably, the hero of the evening was the fourteenth century Provencal Halakhist, R. Menahem HaMeiri, who did take long strides toward viewing trinitarian Christianity as a non-idolatrous religion. From Chakira's report, however, it appears that Meiri's ideas were often harnassed to fit pre-existing ideological positions.
This is not the place to discuss Meiri in full. However, his ideas are important enough (and distorted enough) that before invoking them, people should at least read the discussions by Jacob Katz, Ya'aqov Blidstein and Moshe Halbertal (among others).