Some iPhone apps started out as DBPro projects, some iPhone apps got made into GDK projects. It's really more about design technique - DB is a very fast solution for roughing out ideas for mobile platforms. For instance I made a demo of a game on the PC, and it's being made for iPhone first, then later it'll go back onto PC again for Netbooks. The test applications and editors are done in DBPro - but really where the iPhone etc is concerned, there is no option but to use the official SDK, it's the only way to actually legally release an app for iPhone.
As far as buying a mac and downloading Xcode and the SDK - well it's great, it's a really good development environment, for the biggest mobile phone platform there is. If you can imagine making a couple of grand at least from an app - then it might just be worth investing and seeing where that takes you. Depending on experience of course - I'm not remotely experienced with objective C/C++ but I do have a lot of general, theoretical experience, plus lots of DBPro and BASIC experience - so I think the learning is going smoother than normal in my case.
Android will have more options for indi developers, more platforms that can be developed on, hopefully we'll see a cross platform system for the sake of continuity - an IDE for the mac, linux and windows. Don't really know whats happening with Android though.
