To: [one or more email addresses] Cc: firstname.lastname@example.org Subject: $ [amount] Send!
Certainly, this is not the first request/pay via e-mail option. Gmail has had one for quite some time now, albeit it is a bit hidden as an icon when drafting emails. (It also requires a Google Wallet account.)
According to Square, the Cash method is touted to only require and go straight between bank accounts. I just tried it out myself, and after receiving the $1 test fund in my inbox within seconds, I was redirected to a page to enter "a Visa or MasterCard debit card to deposit $1 from The Square Team" only. No note about a bank account at all.
Personally, that's fine with me but might not be for everyone -- especially those who prefer to just deal with bank accounts and not credit cards.
Square Cash also supports reply-alls on group threads, which means you can request and accept digital funds from colleagues after client dinners and business trips.
Basically, between this and sending money via Gmail, if your friends or colleagues don't pay you back, it's basically your own fault if you didn't make the effort. The only problem might be that there are just too many digital payment methods, from these to PayPal to Venmo and countless more, from which to choose.
And then there's Bitcoin, but let's not go there right now.
Available only in the United States for the moment, Square Cash is supported by Android and iOS mobile devices as well as all e-mail clients.