TV-Be-Gone can work in public places, but it's is not going to work through walls for neighbors.
A spark gap does pretty well. But the FCC fowns on such things.
Unless you manage to aim a strong IR blaster at their window/the ceiling behind it.
Indeed. It works with infrared light, the same way most TV remotes do.
Can you see their window?
Pick up a cheap CCTV infrared floodlight, gut it, and gate it with Ye Olde Bloody Great MOSFET driven by your TV-Be-Gone microcontroller.