Had a brief look at J2ME and PocketJava this week. J2ME looks very mature, and easy to build mobile applications in. Quite simple APIs, and easy to build intuitive and nice looking apps that will run on multiple devices. PocketJava (aka pJava) looks interesting; essentially is a small runtime that still allows you to use all of the JDK. Unfortunately, it doesn't appear to use anything behind JDK 1.1.8.
The one major part that we are missing is a JVM ? for Pocket PC. Anybody have any ideas on this one? Seems like our only option will be to license/buy something, which isn't the end of the world of course.