There might not be a piece of tech more due for an update than the cash register. Enter Square, a payment platform created by Twitter co-founder Jack Dorsey. With the aid of a tiny magnetic card reader that attaches to a smart phone, Square lets anyone process credit cards. It might not do away with paper entirely — plenty of people still prefer cash — but you certainly don't need to wait for a receipt: sign on the screen, and Square sends a copy straight to e-mail.