command-line RTSP client part of live555 library
openRTSP is a command-line program that can be used to open, stream, receive, and (optionally) record media streams that are specified by a RTSP URL - i.e., an URL that begins with rtsp://
openRTSP is one of the test programs of LIVE555 Streaming Media libraries. Live555 is free and open source. It's a set of C++ libraries for multimedia streaming. MPlayer is also part of that suite. VLC uses it for its RTSP client implementation.