RInject is a tool for automated testing of web applications and services. It can be used to test HTTP(S) interfaces for service-level monitoring.
Compared to WebInject, RInject has a more powerful verification- and parsing-engine.
WebInject is a tool for automated testing of web applications and web services. It can be used to test system components with HTTP interfaces, as a test harness to create a suite of functional and regression tests, or for service-level monitoring.