If you look up this manual and the section
Rotax 912/914 Heavy Maintenance Manual section 74 paragraph 3.12:
There are a set of resistance tests that you can perform to test the stator, the ignition coils etc. this tool give you a visual indication on the health of those so you donít have to do the tests (which involve disconnecting connectors and measuring resistance). Iím sure great if you do this several times a week but not if you are an individual owner.