Well...The simplest way would probally be to just mention some links in your inbox...Maybe you could mention that FTP server that will be running next week on your home system, so you can share your photo's with your mother-inlaw...Just point the links back to your machine.
Keep in mind that you will probally have to use 2 or 3 different "misinformation statements" so you can construct an identification matrix. This way you can eliminate false positive caused by routine net traffic. Download something like Ethereal to sniff the incoming connection requests.