Short answer is no - fundamentally iPhone OS uses Cocoa, which is a closed framework only distributed with XCode. Some people have thought about reverse engineering (like Wine) but I don't think anybody has really been successful thus far, let alone use Cocoa as a development environment.
You might be able to create some debian packages (dpkg) that can be run in the background or via the mobile terminal. This is kind of limiting though, because you don't have access to GUI and your app won't be very intuitive.
There seems to be a development platform for porting Blender game logic into a full-fledged iphone game. Maybe you could avoid Xcode this way, but I doubt it.
http://sio2interactive.com/
You could run OSX within Virtualbox/VMWare Player but that's not allowed by Apple.