The folks at Gate want you to know when the postman is coming. Their new product, available now on Kickstarter, is a smart mailbox sensor that tells you when someone is digging in your post box or dropping off letters.The system, which mounts to both traditional “rural” mailboxes as well as in-door “flap” models, pings you when the mail is coming and can even estimate an ETA for your next delivery. While I can’t imagine wanting to know when my mail was coming with any degree of accuracy, there are plenty of people and places where the mail-person’s visit is an important part of their day.