openni tracker not producing any output

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Ideally you should not be required to run any node or launch file to get openni tracker started. ROS openni tracker is a stand alone node. As far as /tf topics are concerned they will only be published once the node has started tracking the user. You can monitor the console output of the program and when it says 'started tracking user #' then /tf topics will be published.

No change is required in 'camera_frame_id' , keep it to 'openni_depth_frame' and while visualizing in rviz keep your fixed/reference frame to 'openni_depth_frame'.

Just in case you want to visualize the pointcloud/depth/rgb images along with /tf skeleton tree , just change the 'camera_frame_id'

string frame_id("openni_depth_frame");

pnh.getParam("camera_frame_id", frame_id);

to

string frame_id("openni_rgb_optical_frame"); // what ever you want here

pnh.getParam("camera_frame_id", frame_id);

Hope it helps, you might want to checkout my posts about other issues while get these things running [http://tayyabnaseer.blogspot.de/2012/04/running-ros-openni-tracker-with.html] :-)

Openni tracker usually publishes the joints of the human skelleton on the TF topic. Therefore your TF configuration should be correct, i.e. links between your fixed-frame and your kinect-frame have to exist. Did you check if transforms are beeing sent on topic /tf ?

You can also visualize tf in rviz and check the warnings if and what transforms are missing...