If you are comfortable writing your own script, it is very easy to make a LaunchAgent that uses curl to check for a file on a site you maintain. Web logs now show you the IP. If you put commands in that file, the script on the computer can take action based on those commands.
isightcapture can be used to take images from the camera, and
screencapture of the desktop (showing email accounts of the unauthorized users).
And of course DropBox. If you keep your important documents there, then you can easily delete them. If you want to transfer images from iSight or screencapture off, you can do so. If you want to transfer images on, or upload scripts that a local agent will run, etc, you can do all that very easily.
MarcoPolo could be used to take a screenshot and an iSight image each and every time the computer wakes up or changes network, and email those images (along with IP) to an email account, which you only need to check if you don't know where or who is using the laptop.