I do work with endangered languages.
Sometimes we get a chance to have a conversation with one of the few remaining speakers of a language, and we'd like to get the best possible recording of their voice, so we can study it later. We'd also like good video of their upper body, as that's an important part of language.
Here's an example, with Yiddish: http://vimeo.com/20128505
Often the spaces are far from ideal - outdoors with wind or traffic, or kids playing in the same room.
Our budget is tiny. We can't afford much equipment. We usually can't dedicate a person to operating equipment - it should be fire-and-forget.
We can't put an omnidirectional mic in the middle, as we need that space to be open. A lapel mic seems like a good choice, since only the fluent speaker's voice really matters, and it's unobtrusive.
We also do a group practice conversation. Here's an example, with Squamish: http://youtu.be/UQImIstZpTM
Would it be sufficient to use a $20 lapel mic, a $20 tripod, and a basic point-and-shoot camera?