In what now looks like a direct, competitive move to combat Google’s latest announcements at their I/O conference, Square Cash announced that it’s not just for brick-and-mortar businesses, but for inter-personal cash exchange as well. It’s starting as an invite-only trial, and works essentially the same way as Google Wallet’s email function. What little is known is that the user will have to CC: Square in the email, and the subject line will determine the amount of cash transferred. Right now, the cost os $0.50 per transaction. It remains to be seen which, if any, of these money transfer apps (Simple, Google Wallet, Venmo, PayPal) will take the lead, but the basic social nature of cash exchange is hot again.