Check it out, the little rubber end-caps that come on some fibre SFPs are detected by a capacitative display! It's only some of them. We went through a pile at work and found that about one in five was able to impersonate a finger. Dunno why it works, but it opens up some great possibilities for a DIY stylus. (Maybe the rubber is doped with an EMF-blocking material.)
The discovery was pretty funny. I was installing SFPs and tossed a bunch of the end-caps on my powered-on iPad for safe keeping. The tablet went nutz from all the multitouches.