Apache Commons Daemon (jsvc) and the New Relic Java agent
The version of Apache Commons Daemon (jsvc) included with Tomcat 6 and available for download on the Apache Commons website does not support many Java 5 jvm switches including the javaagent switch required to start the New Relic java agent. You can read more about the bug tracking the issue.
There is a fix checked into the trunk of the Apache Commons source repository. This page has information on the Apache source repository, and you may find the SVN source repository here.
Additionally, you may also be able to use one of these binary builds of jsvc 1.0.3.
A build of the jsvc daemon from the trunk source will support the -javaagent switch via the -X prefix.