Contactless key fob

Technically possible. Demand would have to be proved though.

With Apple Pay on the Watch and Android Pay being privately tested on Wear (both supporting CDCVM), I’m not entirely convinced it’s worth the money and effort to build a range of wearables.

I will say this, having a small contactless EMV module to put in to costume props is great (think tapping a wand on a TfL reader).