Well, Windows Mobile has a good SDK that anyone can grab, and is open for anyone to develop on, and devices are in market today...I just thought this was an interesting Ars Technica read :)

“Non-disclosure agreements and selective access to development tools are hardly emblematic of an open ecosystem. Google has intentionally disadvantaged many developers and kept the broader Android community in the dark about the progress of the platform. Google's failure to fulfill its commitment to openness has eroded one of the principle differentiating factors that made Android a relevant alternative to Apple's iPhone operating system. If Google cannot change course, the lack of transparency in the development process will likely push disenfranchised developers towards other mobile platforms.”

http://arstechnica.com/news.ars/post/20080715-googles-android-platform-not-so-open-after-all.html