Since getting an iPhone some months ago, I'm been thinking that I don't need a stand-alone GPS, a digital camera, a land-line phone, a digital calendar, and other things. Now Yahoo Finance has a list of 10 devices that smart phones are replacing: PDAs, video cameras, MP3 players, digital cameras, handheld video games, GPS, PCs, regular cell  phones, watches, remote controls.

That's the list. I would add Kindle or Nook to the list with the IBooks app. Others come to mind: outdoor thermometer, compass.

See also "15 Things you can control with your iPhone."