The GBA tracer functions almost the same as the Gens tracer, in terms of the hook_log function.
Some info to help someone get decent info out of the logs:
Example:
hook_wr1 1 0200DACC 0200DACC = Logs any instruction that writes to 0200DACC to hook.txt
hook_rd1 1 0200DACC 0200DACC = Logs any instruction that reads 0200DACC to hook.txt
Logging all instructions when logging hook.txt entries is preferred, because you can see all of the instructions that led to the hook.txt entry ending up the way it did.
'/' = toggles instruction logging to 'trace.log'
'.' = dumps BG info, RAM, CRAM, VRAM, WRAM, SRAM
',' = toggles memory logging to 'hook.txt' (set by 'hook_log.txt')
I've included a replacement file for hook_log.txt that has a small amount of basic usage information included in the file in the form of comments.