Troubleshooting

TF complains that transforms don't exist or require extrapolation into the future.

This is almost always a time synchronisation issue. To verify that it is a time sync issue, check rosrun tf tf_monitor to make sure that you're transforms are being published. If they are, check rosrun rqt_tf_tree rqt_tf_tree to make sure the transforms are connected correctly. If everything looks okay, it's almost definitely a time sync issue, checkout Time Synchronisation.

The launch script keeps selecting the local node instead of the remote roscore.

If the launcher script (or roslaunch) has been run on the Pi-puck when a remote roscore was not available it may have left behind a local roscore instance which is being used instead. Make sure the local roscore is no longer running, or manually specify the remote roscore.

Python says it can't find the module madgwick_py.

You've checked out the repository without submodules. You just need to pull in submodules and that should fix it.