Gob smackingly in love with this idea. Some clever people known as Teevio and Beste Miray have created this template for making personalised envelopes that interface with Google maps. Brilliant!
Pick any address in the world, add a caption that tickles your fancy, and hit preview. What then opens up is your creation in an envelope template that you can print out, cut, stick up and send.
Oh I rest easy knowing that there are clever people like this in the world! Do go here and have a play.