A friend at work has been raving about geocaching for a few months now, and has just set one up in Lincoln in relation to Boolefest.
I just had a chat with him about what it is and how it works, I was planning on explaining, but then I found this video that kinda does it for me:
It's pretty simple to set up, and could be an interesting addition to this idea of connected locations and user interaction.
It's doesn't just have to be about finding treasure, but can be run as a pass the parcel exercise. It's found initially and then taken to the next point, found again and taken a bit further.
I could set up a geocache in Stortford and either get it set to Lincoln or perhaps more interestingly to Villiers-sur-Marne en France.
Time scale would be totally unpredictable and down to the geocache hunters, but I think i'm going to give this a go.
Here's a LINK to the website