Features:
- no AI whatsoever
- no weapons
Problem targeted:
Sneaky Grievers hiding behind North-/Westwalls, Trees or whatever, trying to run into your homestead once you open the gate, which is a nothing but a sideeffect of the isometric game-engine.

Takes a load of Boards and Blocks + Ropes/Fibres and/or Metal.
Can be build everywhere, should be build next to your gate, because it does this:
[climb up]
*Sandclock appears*
Eiter
[Textmsg]There are no/x non-kin Hearthlings within yy (30? 40? 80? ) tiles radius of sight [/Textmsg]
or
Drowsing Rod like Circle, showing above.
[climb down]
Walk happily through your door.
Alternative use: Scout your enemies during a siege.
Flame on.