The German Pokemon Ruby is the debug rom and it's pretty fun to screw around with. To enable debugging options, hit select at the title screen or press R+Start on the overworld during gameplay. It does get a bit confusing to navigate sometimes but the guys at tcrf.net are doing a pretty good job at documenting it on their wiki. There were some people who said they were having trouble getting it to boot in VBA, so set the save type to flash 128k and it should run normally.