Chatterous is group chat combining the web, im, email and your phone. You can create groups of friends to chat together, but your friends can use their preferred chatting software--no need to even join Chatterous. The Chatterous API lets you access and edit members and groups, as well as send and search messages. The API is currently in public beta.
The following is a list of SDKs from our SDK directory that matched your search term. Though your definition of an SDK may differ, in our world, we define SDKs as platform- specific tools for consuming existing APIs of the sort we list in our API directory. For example, the Ruby SDK for consuming the Twitter Ads API. If you think an SDK, API, or other asset is missing from our directory, be sure to check our guidelines for making contributions to ProgrammableWeb.