I'm pretty sure fHostileActorInteriorDistance and fHostileActorExteriorDistance are what the engine uses to tell the player they cannot sleep because enemies are nearby, etc, but what would be the scripting equivalents so I can create conditions in my scripts to test these?

This is for that "stalk your player character in their bed" mod, right?

Hrrrrrrrrrrm.

Possibly not the best solution, but - and this reflects the fact that I've only done work with spell scripting! - you could force the player to cast a custom spell with the radius you want, the spell having a condition of Target GetShouldAttack == 1. If any targets are affected, the spell fires a script that increments a global variable by 1. If the global variable is non-zero, the script will not progress further and let you know that enemies want to Do Things To Your Dead Body. Then it resets the variable to zero in anticipation of the next test the player performs.

Yes, findclosestactor then ishostiletoplayer, that will give you closest actors that are hostile towards you.

FindClosestActor wouldn't work:

1) It will return the player if the player is the closest.
2) Even if it didn't, if you had one friendly person close to you and then like seven enemies a few yards away, that check would fail to catch the hostiles.

True, try it with random and keep looping it, sometimes it will catch friends but other times it will get foes.

AstralFire's suggestion should work. The quest/alias alternative would be to start a quest with an alias set to be filled with the nearest hostile actor, and then check 1) if the quest has started and 2) if the distance to that alias is within the appropriate game setting.

I wonder if IsInCombat on the player would work? When enemies are nearby is the player considered IsInCombat?

That's a good idea. I do know that just having a dragon arrive makes it so a player cannot get on the carriage as it says "Can't board while in combat."

I don't try waiting very often, but it seems to me that that would work any time the enemies are showing up as red dots already, and IIRC Wait has more stringent restrictions than simply not having red dots on the radar.

I'm pretty sure functions like IsInCombat are only used for AI, because a combat state is something the AI goes into, while the player has no such detection (since you can have your weapon out and swing but not really be "in combat"). I assume then, IsInCombat simply checks for that state on the AI.

Of course I could be wrong.

Edit: Guess I lied just looked at my perk again and I'm using GetCombatState == 0

IsInCombat works on the player. I believe it should return true if there is an enemy actively engaged in combat with the player (red marks on the compass, exciting battle music, etc.)

My testing has been limited, however.
I'm using it in an allow dual cast perk to keep the player from dual casting certain things in combat.

I tried IsInCombat for player and it worked.
Although the player would have to 'knows' when he is attacked (like red dots appeared on compass)

IsInCombat is quite handy when you want to include sneak-check on your script