I've thought about that, I wanted to do it in Java for that reason, so it would run on linux/windows/mac
the problem with doing that is codec installers. Java's support for media files is at best poor! divx, realplayer, mp3's and all those need to be external players. So I guess a Java app could use external command lines that are configured, but I fear the multple OS testing.
The second issue is using a GPS app. Again, Java can do this for windows using some ActiveX interfaces etc. But this will be a different game all together for macs and for linux.
I'll give it some thought again, to see whether or not it is a viable option. I'll try a few proof of concepts first but I'm doubtful in all honesty.