Ubuntu and Wine on ARM and Windows Mobile
As far as applications are concerned, Windows Mobile isn't all that different from Windows itself. The Windows Mobile API was designed to be as close to Win32 as possible. This means that getting Windows Mobile apps to work inside Wine isn't that much of a stretch - the code changes may even be trivial, at least for Windows Mobile apps on x86.
The harder task is porting Wine to the ARM architecture, where Windows mobile still commands a sizable marketshare. This likely requires tweaking code in wineserver and a few of our core dlls. This may actually be an easy task for someone familiar with ARM - currently no one's really tried it, since Wine developers don't know much about ARM.
Porting Wine to ARM and Ubuntu Mobile
The ultimate goal, of course, is to be able to easily bring a Windows Mobile application to Ubuntu-MID. Wine is not a large piece of software (less than 15 megabytes), so it could easily fit on most mobile devices. The fundamental differences with Windows and Linux applications are also not as big of an issue, as mobile applications tend to take up the entire screen and generally not interact much with other applications.
It's important to remember that this includes free applications as well as proprietary. We might even be able to attract a large vendor to Ubuntu Mobile if we make their custom application originally written for Windows Mobile a first-class citizen. That's way better for Ubuntu's future than there being yet another Windows smartphone.