Have received a description of a possible B&B/apt. homestay arrangement in NYC and it says "one bed magnetic." What is that? Do I need to remove my watch to sleep in it?

Why not just call the B&B and ask???

One guess: Some chiropractors use magnets for "healing" (use your own judgment on this one). And I've heard that there are beds that have magnets embedded in the mattress, which is supposed to be therapeutic.

"use your own judgment" was an understatement.
another snake oil ruse like using crystals for their 'healing powers'.

I know a woman who sells magnetic products. Magnets are supposed to have healing properties to give you more energy, relieve stress, etc. My husband is currently wearing magnetic insoles in his shoes. Anyway, the magnetic bed is probably a mattress with magnets inside which will correspond with reflexology points on your body. You won't even be able to feel them, and no, you won't have to remove your watch.