"you have to be within 100 metres"
What if you have a directional antenna? Probably also need some really good binoculars too, and maybe a friend to keep the antenna aimed on-target while you guide it on its unscheduled voyage. Assuming you were the sort of nefarious prankster that would do such a thing. Which you're not.
Of course if the xbee link is hackable it's probably moot.