These guys,Touch-Screen Elkskin Ropers :: Aerostich/RiderWearHouse Motorcycle Jackets, Suits, Clothing, & Gear make some gloves that will work with a phone screen, don't know how well they work. Maybe other Glove makers will follow.
Andy - hasn't so far. That gorilla glass is pretty hard and copper wire is pretty soft....plus only the gentlest of touches is required to make the screen work... Only problem is, you're a bit f*cked in bad weather. I stick a zip-lock bag over the screen or remove it from the mount and stick it in my pocket, relying on the audio in my headset for directions...works pretty well.
Cool............at least when your scrabbling to put the iPhone away as the rain starts you can console yourself with the though of the cash you saved not buying a dedicated GPS