This tool is simple and fairly precise if your keeper is in weak or better form.
You just need to fill in the current TSI and select the form of your player in the drop down menu.
As a result you are told how far in training your keeper is.
Thanks to kolmis for linking to this tool from FoxTrick. If you don't use FoxTrick already then you are missing out on a lot, go download it now! :-)