You could write a script that parses the output of aticonfig and run it every x seconds. For example,
aticonfig --adapter=ID --odgc | grep 'GPU load' | awk '{ print $4; }'
will give you the load. If it's not 99%, card is not used...
I just watch the temps to make sure there is a load.
watch -n 2 aticonfig --adapter=all --odgt
here is a couple of commands that I have in a file that I always use.
aticonfig --od-enable
aticonfig --adapter=all --od-setclocks=920,400
aticonfig --adapter=all --odgc
DISPLAY=:0.1 aticonfig --pplib-cmd "set fanspeed 0 70"
DISPLAY=:0.3 aticonfig --pplib-cmd "get fanspeed 0"
for i in 0 1 2 3 4; do DISPLAY=:0.$i aticonfig --pplib-cmd "get fanspeed 0"; done