I feel lame when it comes to mobile phone hacking because I'm so far behind the state of the art, by at least five or more years. The only good thing about this is that, generally, only games have taken off on phones, leaving the universe of practical applications almost untouched. This is a newb article, so, if you're experience, go away :)
The problem with programming J2ME devices is that there are so many devices, and they generally support a different subset of J2ME features or APIs (called JSRs). I recently got an LG600g and found out that it's a junk phone for Java hacking. It doesn't support many JSRs.
I wanted to try writing code to extract data from the PIM. No such luck, because the PIM JSRs aren't supported on this phone. In fact, few JSR are supported. A little sleuthing revealed that this phone looks like an LG KP210.
LG documents the JSRs supported by the KP210 on their developer site, developer.lgmobile.com. There, you can download SDKs for LG J2ME development.
A similarly priced (cheap) phone called the Motorola i290 from Boost mobile is a different story. If you go to the Moto site, there is a complete SDK for the i290, and a lot of different JSRs are supported. Moto is very programmer-friendly, and they have an exemplary site.
Regardless, I'm stuck with the LG until the minutes run down. So, I'll program for that, for now. The limitations are a challenge.