I think the most simple way to achieve your request is using a transparent sprite bigger than your Player gadget, pinned, so, check if this sprite is overlapping what you want, because if you start to check each distance, your game will slow down a bit.
Doing your second request:
> Wasps is overlapping the transparent sprite:
>> Change his sprite for Flying;
>> Move for where your want (use SIN for natural movements, or in line, just checking the Player position and then making his trace route for there), setting X and Y (click inside that second window and select the player, then, select the Player.X and Player.Y);
I think if you wish make them go to the player, you'll need make the Wisps a little bit dizzy on the path, or they will run directly to the player, making his movement unnatural.