When away I use a vpn connection to connect to my home server. The first thing after connecting is usually mounting some resources using sshfs (yes I know, not very efficient but for personal use is more than enough). I wanted to automate that and so I dug a bit around NetworkManager.
Apparently all you have to do is drop a script similar to this in
#!/bin/bash interface=$1 status=$2 LOG="/var/log/network_manager_custom.log" if [ "$CONNECTION_UUID" = "xxx-xxx-xxx" ]; then case $status in vpn-up) mount /mnt/something >> $LOG 2>&1 ;; vpn-down) umount /mnt/something >> $LOG 2>&1 ;; esac fi
Make it executable and be sure it is not world writeable.