IBM's Spoken Web is just such a solution that is accessible from any kind of phone. Spoken web is a technology by which voice sites are implemented much like on the Internet however contents are restricted to voice contents only. User can either just retrieve information or also interact with one another by posting questions and answers.
Soon and I actually managed to set up our own voice-(test-)site which we later accessed through a different call-in number to see how it came out.
Apart from trying the various functionalities of Spoken Web we also had our first meeting with local SEWA staff from the Ahmedabad district which had been set up just a day earlier. Soon and I were very glad to a have a chance to speak to someone from the SEWA district as so far our use cases have been based on our understanding of the situation and on our own experiences. Speaking to him helped us a great deal to understand how the processes for new member registration at the SEWA offices actually work.