There is a very simple C++ sample application available in pjsip-apps/src/samples/pjsua2_demo.cpp. The binary will be located in pjsip-apps/bin/samples.
This is a rather complete Python GUI sample apps, located in pjsip-apps/src/pygui. It requires Python 2.7 and above, and the Python SWIG module of course. To use the application, simply run:
Please see https://trac.pjsip.org/repos/wiki/Getting-Started/Android#pjsua2 for Android sample application.
There is a Hello World type of application located in pjsip-apps/src/swig/java. This requires the Java SWIG module. After building the SWIG module, run make test from this directory to run the app.