The touch sensitive display for the iPhone (and iPad) uses an electrostatic screen, there is a great article on this in How Stuff Works. The key point is that a glove interferes with your finger delivering the electrostatic charge necessary to register on the phone.
In an earlier post I talked about RunKeeper as one of my new iPhone app favorites. However, one issue you quickly realize when you use an iPhone and it is cold is that the device doesn't work with gloves! For people like me that enjoy running outside this means to stop and start the device you need to stop, take off your gloves, and then touch the screen to stop or pause the phone.
Of course, the people at Apple live in California so this is not a big problem for them, but in places that experience winter you need gloves. This is a broader issue in thinking about the human computer interface for devices as we rely upon new touch sensitive interfaces. The web site BoingBoing shows how some enterprising Koreans found using a mini-sausage as stylus worked.
I stumbled across an interesting review of four different glove products that work with iPhones when using the Flipboard app for my iPad.
Review roundup: Four touchscreen-compatible gloves:
http://www.macworld.com/article/156543/2011/01/touchscreen_gloves_review.html?lsrc=rss_main
For those like me in Maryland suffering through the cold I thought I would share, I went with the Aglove product. Please let me know if you have tried any of these, when I get mine in I'll let you know how they work-- jack@umbc.edu.