gkrellm will automatically use nvidia-settings IF IT FINDS IT to determine the GPU temperature. If there is an nvidia use variable, would such a construct make sense?
RDEPEND="nvidia? ( nvidia-settings )"
Is the nvidia use variable used at all?
As an alternative, perhaps a message at post install could be issued for the user (testing for nvidia) that if they want GPU temp to show that they need to emerge nvidia-settings?
4 months no action. I'm not a dev, so can't fix.