Yes! The Smart Change Detection feature looks for the text in the Start text box, then the End text, then compares the text between those two against what it had the last time it checked.

This is useful to detect changes in a portion of the page, but can also be used to detect unacceptable changes.

The usual way to do that is to just provide a Start text block, and not an End one. Then if the Start text isn't found, that is a failure.

So for example, if you do a telnet Script-based check, you'd want it to be considered a success only if this is output:

Escape character is '^]'

So you'd put that in the Start text block, and leave the End block empty.

Then if that text isn't found (as would occur if telnet couldn't connect to the server), Simon will log a failure.