On-deck applications

There are a number of on-deck application frameworks that can be used for developing mobile applications. Some examples include Java ME, Windows Mobile, Google's Android phone, Symbian applications etc. Some of these frameworks are more widely supported across and range of mobile phones and some are specific to certain operating systems on the phone. Determining what to develop your application in really depends on which phones are more widely used. This information can normally be obtained off the web or from the mobile network operators.
One you decide on the application framework you will need to look at the differences in screen resolution for the phones used by your customer base.
For the above reasons on-deck applications are difficult if your application has a wide user base. Java ME is probably supported my the widest variety phones, but ways to managed the screen resolutions will need to be built into your application. In the past the Java classes present in the virtual machines differ from one phone manufacturer to the next. This adds to the complexity of your deployment because classes might be missing or clash with existing ones. The bottom line is that there is an ongoing overhead to test new phones as they become available and manage the screen resolution and packaging differences.