Sending lets you send a small message to anyone on an plane. And there's 0 failure chance for the same plane. It's only level 4 for clerics. Not really that high considering everyone else is communicating by carrier pigeon or mounted couriers.
It takes 10 minutes so you can stop the underboss from conducting a sending informing the big bad that you're breaking his stuff.
RC says that wands and scrolls use the same casting time as the stored spell. Which is why wands of nerveskitter work.