To be honest, while not often. The fact that players will idle can get on both the Neighbors and the other team's nerve. Thus I recommend a perfect idle preventor. Imbir!
Starting off, if players stay in a hiding spot for far too long (like under the stair way by the basement or just standing in spawn for a few minutes.) Imbir will spawn and begin to meow, attracting the attention of the neighbor to the idling kid perhaps with an audio and visual cue. (this can of course be tweaked.) Imbir can also be shooed away of course like crows.
You may think that if you're in a closet you'll be safe but not anymore! Imbir has grown wise and if you're in a closet for far too long (there's a meter that slowly fills up and being out of a closet will lower it, it won't instantly go down if you open and close the door) Imbir will appear in front of the closet and jump up before opening the doors. This will open the kid up to being detected on the sonar and soon enough Imbir will indicate that they're idle by meowing.
If it's too odd, then perhaps Imbir will only open wardrobes to prevent trolls from delaying rounds via hiding.