I have been building kernels on my imac in virtual machines. This can take a while and I wanted notifications when the build had finished running.
On my imac
$ while true nc -l 4000 | say done
This makes netcat(1) wait in a loop for any connections then pipes the output into say(1).
On the vm
$ make buildkernel; echo "Build Complete" | nc -N imac 4000
Replace imac with the hostname or ip of your machine.
I have seen the build side hang and not close the connection until killed, I am not sure why.