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Welcome to the forums @LW57 and thank you for your help dear @SunsetRunner! 
The magnets vs. Fitbits combination depends on the type of magnetic device you're wearing; the type of tracker you own and the proximity/intensity within eachother. Electronics and magnets have a tendency of not mixing well, specially if there's a screen.
There is definitely ferromagnetic materials in Fitbit trackers and there is definitely the potential for damage just like when any other electronic device comes into contact with magnets. However; this depends on context of the magnetic device; for example, a balance magnetic bracelet or necklace has a low magnetism and wouldn't cause an effect on your tracker; you'll need to double check the intensity of the magnetism of your gloves to be certain they are safe to wear.
Hope this helps! Let me know if you have any questions 
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