Oh yeah, my iPhone 3GS is definately a permanent component of my EDC and for more than the built in digital compass. I have Cody Lundin's 98.6 degrees, John and Geri McPhersons Ultimate Guide to Wilderness Living on my Kindle App along with various first aid guides and encyclopedias. Also scans of personal documents in my PDF reader and even just fun reading material for staying in place waiting for rescue. For urban survival I'd recommend everyone have some sort of PDA as a primary part of their kit, just remember carrying personal data that way can be a security risk too. Any PDA out there today has some kind of passcode security available for it, you should definately make use of it even if its just a simple keypad lock.