DeSilva is right, but let me expand on that idea.
Use SUN's WTK to build your application. Most all new phones have the MIDP2.0 spec so I would focus on this standard, and not try and support MIDP1.0
Make sure your app adjusts it's screen presentation to the phones. This will require taking into consideration that the range of standard phone screen sizes range from 96x96 pixels to 240x320 pixels.
Making network aware apps on the phone is not easy, especially when there are firewalls, and Single-Sign-On (SSO) features to many sites. As long as you can use a standard HTTP or Socket connection to the server you will do okay.
One
word of warning, most cellular service providers are jerks, in that they don't want to provide much, if any, help to developers (that would cost them money), and they don't think their locked down systems are an impedence to development. So if you can't do it yourself, and you don't find help on forums like this one, then you most likely aren't going to get it to work.
Also just because a phone maker (nokia, motorola, sony-ericsson) say thier phone supports JSR-xyz, doesn't mean that the cellular service provider will allow that support to be functional on the device.
And finally, if you have to sign your jarfile, you will need to get a verisign Root CA signed cert. This goes for the web SSL cert that is needed for HTTPS connections. However I am having an issue with the IBM j9 vm supporting even that. So beware, and YMMV.
Best Wishes,
-Shawn
