GupShup is a SMS service from Webaroo, a startup based out of IIT Bombay. It lets you create your group and invite friends to join it. Send a SMS to the group and all the subscribers of the group receive it.
At first I likened it to Twitter or Jaiku. However, I think it is closer to the emailgroups model. You can create your own group, moderate it and a SMS to the group reaches everyone. Twitter and Jaiku let you broadcast, that is to everyone if you want to. GupShup is more of multicasting.
Where can this be useful? It can be extremely valuable in the Indian context. The mobile and phone network are more popular than the computer and the Internet connection. Sometimes economical too. A lot of times easier too. This can save costs for people who need to communicate using SMS, since now you can replace multiple SMSs by just one. You can control visibility of the messages and the public groups are visible on the Web too. There are even feeds available for public groups. However, GupShup is primarily for mobile users.
Will I use it? Probably not much, since I have the Internet already available, and most of my friends are online too. However I can think of many people who can effectively use this. Think of this. A group for monitoring traffic conditions in Mumbai, with members sending SMSs to report bottlenecks or traffic jams. Or think about someone wanting to send out deals everyday. Or a manager communicating with his/her sales agents in the field. I think it can be really useful.
I am not sure of the business model, it is probably advertisement based, but the service is free to everyone currently. I think that a paid version might also work for corporates. The only doubt I have is whether a flourish here will cause problems in the mobile networks, which are known to freeze for every overload. If not, this can a very valuable service.