Available as of Camel 2.13
See the JSonPath project page for further examples.
You can use Bean Integration to invoke a method on a bean and use various languages such as JSonPath to extract a value from the message and bind it to a method parameter.
To use JSonPath in your camel routes you need to add the a dependency on camel-jsonpath which implements the JSonPath language.
If you use maven you could just add the following to your pom.xml, substituting the version number for the latest & greatest release (see the download page for the latest versions).