Paul Raine, developer of Zengengo, is talking on developing apps for language teaching. He is in Japan, along with two other of the Sig members, some are in NZ, and the rest Australia. He is discussing how to develop mobile versus web applications. As well as being a teacher and entrepreneur, he has published academics papers on language learning, and a series of webinars.
An import point Paul made was that web based products need to have a source of revenue. Edmodo recently shut down due to a lack of advertising revenue.
Paul suggested you don't have to throw away the Learning Management System investment, such as in Moodle, but can add new functions, for example language learning.
Paul is getting into the theory, with Vygotsky's Zone of Proximal Development (ZPD). The practical implications of this is that students need help to learn, step by step.