I'm looking for a way to store debug output to a file, along with a simple method to retrieve the file from the phone.  Is it possible for a midlet to write to the system messages file?

Currently, MIDlet can use System.out.println() and system.err.println() to write traces/logs. We do not provide separate API/location to store api. All the ourputs of System.out.println() and System.err.println() goes to device syslog messages Those syslog files can be extracted using device Web intetrface.

Although a midlet does have some access to storage space in the phone, I don't think that is accessible from the web page for down load. Normally if people want to keep the syslog fils on the phone, you enable the "Preserve logs" setting on the trace settings page, and then any log files would be written to nvram and can be downloaded later