Zyphen:
"Wake me if any person, creature, or entity that is larger than a hare and that is unknown to me ventures within the bounds of this campsite (as delineated by the current position of the string-with-bells setup by Zyphen, and extending up into the air 300 feet and down into the ground 50 feet)."
OK, since I didn't have time to post anything for a while, I just went with my original idea this time. But for the reference for the future...
This spell does not work on anything that the Spellcaster himself cannot himself observe. So, for example, because K doesn't have Darkvision or Low Light vision, anything that happens in the dark won't trigger at all. Same goes with hidden creatures or invisible creatures. Or events that depends on really far away.
So into the ground 50 feet, and up into the air (further than the camp bonfire light extends) are pretty much out. It's gotta be some distance K can see. String and bells should be OK, but it'll only be something that's based on sounds (that's audible), and thus we can't probably distinguish what sort of creature/event made that sound.
-K