Square Cash is all well and good if you want to send money to someone right away, but what if you want to set something aside for later, such as paying back a friend? You're covered after today. Square has updated its Android and iOS apps to introduce the optional Cash Drawer, which holds on to the money you receive in one handy place. In other words, it's a bit like PayPal and other digital wallets. You can withdraw money whenever you need it, and you'll soon have the choice of adding money from your own bank account. And don't worry, this is optional -- if you use Square Cash precisely because it's not a go-between like PayPal, you can carry on as usual.