Dotsub - alternative to Yappr

Aha, I've just found out from Nik Peachey's blog that Dotsub is similar to Yappr but you don't need to pay a subscription fee in order to input subtitles beneath video clips i.e. students can transcribe video clips for free! One idea of Nik's is really fab - you can ask students to create their own video clips (with digital cameras or webcams), upload them to Dotsub and then get other classmates to transcribe them.
I would add that you could then get students to embed these transcribed videos to their own blogs and then evaluate each other's contributions through the commenting feature.
Nik's idea could easily translate into a group project which has enormous potential for developing students' all-round English skills. Just think of the possibilities! The video clips could be based on a topic or based around a target language structure that is currently being covered in the syllabus, thus reinforcing what they learn (if indeed, they do learn!) from their (may I dare say, mundane) textbooks. I think my P6 class could handle this project as long as I put them into mixed-ability groups (interestingly enough, those that I consider to be tech-geeks also happen to be above-average in English - I know who they are because I did a survey with my class when they were in P5 last year). However, one problem that would most likely occur in this scenario would be the unequal contribution by individual members of a particular group. Or, even if the students did take equal turns to transcribe a video clip, how would you deal with the technologically or linguistically inept? One would have to figure this out in advance but for starters teachers running this project would no doubt need tonnes and tonnes of patience!