This wrapper is meant to use curl in an OOP manner while preserving the programming style / API style of libcurl. This is more like an object oriented c++ bind rather than a wrapper, as it tries to keep the api as simple and as close to the original as possible without wrapping unnecessary stuff.
Paul Thomas's Performance Tuned SSH, aka PTssh. A cross-platform, high-performance, multi-threaded, thread-safe library implementing the SSH2 protocol and SFTP version 3.