Buying a video doorbell is worth it for several reasons. They’re convenient if you get a lot of deliveries or visitors, as they let you glance at a phone alert to decide whether it’s necessary to drop everything and go to the door. They can provide peace of mind, too, particularly if you’re heading out of town on vacation. Fortunately, Google’s entry-level Nest Doorbell — one of the best models available — is on sale for $139.99 ($40 off) at Amazon, Best Buy, and Target in the…


