If you like Replay Media Catcher, you can use Replay Video Capture or upgrade to Replay Capture Suite that has both Replay Media Catcher and Replay Video Capture.

Replay Video Capture and WM Capture are screen video capture programs. The quality is better when you rip/download/capture streaming videos using software like Replay Media Catcher. But screen capture software can record more streams.

Replay Media Catcher can't be detected only when you use its Web stream Dumper, that works with HTTP streams only.

The only way to record Silverlight videos I know is by using screen capture software.