I wrote a small Tensorboard callback to visualize the metrics and the parameter/gradient distributions and histograms: https://nbviewer.jupyter.org/github/MicPie/fastai_course_v3/blob/master/TBLogger_v2.ipynb
It is still a work in progress, because the code needs to polished and is only tested with the network in the notebook.
Could this be interesting for the library? If, how would I best incorporate the needed Logger class (with the Copyleft license)?
Feedback, suggestions, tips, and etc. are highly appreciated! 
PS: I don’t know if switching to TensorboardX would be a better choice. Maybe somebody worked already with TensorbordX and can share his experience?