The phone obviously has functions/methods to call to get this info to display it in the status bar, but from searching around it seems like Apple doesn't allow it (i.e. private APIs) from everything I've read on the developer site.
I too have seen apps that can tell WiFi network strength and battery status (time doesn't really count, that is easy is every software environment I've ever dealt with) and am a little confused by this because all official word seems to say this isn't supported. I found some references to private frameworks on code.google.com to help with WiFi related info. So what do you guys think, are these WiFi/battery status apps breaking rules in the use of private APIs and somehow Apple didn't notice during the approval process or do you think there is some undocumented work around that Apple considers legit yet unsupported? I'd really like to be able to handle battery, WiFi, and cell info in my own way in some of my apps but am a little nervous about wasting much more time pursuing a solution to have Apple tell me I can't do it when I submit my app.