Before I dive into Windows Mobile, I must first disclaim that I'm a relatively big fan of the .NET platform, usually by means of the Mono Project. The .NET Compact Framework (referred to as .NET CF) is merely an extension of the .NET framework meaning you can use a lot of the same code and know-how for developing Windows Forms interfaces for Windows Mobile enabled smart phones as well as already existing code for the backend of your embedded application (there is also an interesting extension on .NET CF available at OpenNETCF). The power of this sort of portability should go without saying, but why not say it anyways? Because of .NET CF I can write the same services and network interoperability code that can be used in my desktop application and take it straight over to my embedded application with zero or minimal hassle (optimizing your bloated desktop code for an embedded application is always a good idea). In addition the normal trimmings of .NET, the Microsoft.WindowsMobile namespace offers a myriad of device-specific APIs for sending messages, interacting with a smart phone's contacts, calendaring, camera, media player and all the rest that comes stock on modern Windows smart phones. With a saturday afternoon spent in an empty office pouring over API documentation and hacking furioiusly on some test applications, I could send messages, take pictures, play with contact information and do some G-rated damage to a Windows smart phone (Rory Blythe's screencasts on the subject are a fantastic resource as well). The obvious downside is that it is Windows (Mobile) and that the consumers that tend to own Windows smart phones tend to be business types who walk around with suits and have the word "synergy" tattooed on their buttocks. Not my cup of tea, nor my target market. Next!
On the other side of the world to Nokia. Nokia's S90 platform is expansive to say the least, and runs on quite a few devices as well. While I'm certainly not "in the biz" with regards to mobile device development, the sheer size of the entire S90 platform and the varying means of using it surprised me. Nokia's S90 platform builds on top of Symbian (ick!) which, fortunately, powers more than half the mobile market but, unfortunately, sucks. You know it, I know it, even Symbian Ltd. knows it, so let's stop pretending. With regards to Nokia's developer tools though, they offer a relatively stock Java API for developers to use (eSWT? gross!), their Carbide C++ framework which builds on top of Symbian's own C++ libraries, and even a Python API for their SDKs (the Maemo work is worth a look too). Most interesting to me was their Open C project which borrows some of the best bits and pieces from a few open source projects and brings them to the mobile platform. While Nokia obvious doesn't have a clue with device design they do seem to be with it in terms of the open source world. Open C is built primarily on top of OpenBSD and OpenSSL libraries with a bit of libz and GNOME thrown in there as well.
Either somebody at Nokia really wants to piss Theo de Raadt off, or they have a high opinion of his work! Personally I wouldn't have chose OpenBSD, but their unwaivering committment to the "absolutely open source" ideology seems to make their projects an ideal fishing ground for commercial ventures who are really looking to stand atop the shoulders of giants.
Even Blackberry has tools readily available for developers, but I can't say I've researched them too much. I'm pretty sure that people who develop applications for Blackberries go sterile or get cast outside the universe at armageddon or something.
The device development world is riper than ever for some killer application development, the Opera guys seem to get it (they use Qtopia from what I can tell), the Google guys seem to get it, where are the smaller shops? If the iPhone turns out to have some sort of "Cocoa Mobile Edition" (a poor ripoff on my part from JavaME) then I think we will see an influx of Mac independent developers to the iPhone as a platform all battling for a tiny niche of a niche just as they are on the Mac platform. What about the entire rest of the mobile market?
With the growing ubiquity of the mobile devices market the opportunity for independent developers to write killer applications for Windows Mobile, Symbian, embedded Linuxes, and possibily the iPhone, is more attainable than ever. The tools to develop are either free or cheap, and you don't necessarily need to be a hero-programmer to develop applications for these embedded systems anymore either.
That said, Brent, I'll buy you a beer when I see NetNewsWire iPhone Edition.