This is a simple webapp that shows how to do the oauth jumble and read data from the Fitbit API. It does almost nothing, just authorizing with fitbit and then displaying your steps of the last 7 days on a graph.
Register a desktop application and copy your applications consumer key and secret.
Download the latest release JAR, open a Terminal and type this:
java -DCONSUMER_KEY=XXX -DCONSUMER_SECRET=YYY -jar fitbit-webapp-example-0.0.1-SNAPSHOT-jar-with-dependencies.jar
After that, open a browser and point it to http://127.0.0.1:4567 - that's it.