Basocally, if the siren is activated, a squadron of varying size and type of bombet planes will appear within a mile of the object and proceed to bomb the crap out of the immediate area. Bomb blast craters will inexplicably vanish after about a week and the horn itself is not damaged by the explosions.
To me, the idea does not sound promising, for three reasons:
1. It's not subtle. Bombers and bombs coming from nowhere? How the hell does ANYONE cover that up? I'd love the historical background justification for this object.
2. It sounds very useful. All you'd need is a way to remotely activate the siren, and you'd be able call airstrikes anywhere. As a big fan of the Shock and Awe style of military warfare, let me tell you that being able to call airstrikes anywhere is a wonderful thing. However, pretty much every other useful SCP in these archives has some kind of a cost. The obvious cost for this siren is "you get bombed too," but that can easily be avoided.
3. The bomb craters just vanish? Have you thought this all the way through? What about damage to buildings? Or people?
Now, that last point might be this idea's saving grace. What if all the damage the bombers did to the landscape and buildings vanished, but the other casualties did not? It'd be quite something, to have a squadron of Badgers fly over your down and blow most of it up, killing hundreds, only for all the actual evidence of a bombing disappear a short time after, leaving you very, very confused.
Yeah, a cool idea, but definitely add some kind of cost, and some reason why it hasn't been noticed. Maybe using it dooms you, or drives you insane, or gives you the worst stubbed toe of your life.
Also, is this some kind of time warp thing? Is it always the same bombers, flying the same pattern, dropping the bombs in the same locations relative to the siren? Or do the bombers vary? Maybe over the years they have updated to fit the latest types of bombers.
This could be a cool concept if you can work it out to be cool but dangerous.
i was thinking it could range anywhere from German BF109s to American Flying Fortresses. Maybe they only effect certain kinds of buildings? Maybe only buildings from the era?
What would be cool is if the bombs fell from nowhere (no planes), and one bomb always hit the person who activated it, no matter where they are. Craters and damage should just stay normal (no disappearing).
Another possibility is to make it Memetic, simulating a bombing right down to physical effects only for the people that hear it, throw in a radio log of someone calling for help the midst of a "bombing" and it could be nice.