Coffee and its Effects on Feature Creep (2011)
In Denmark, the biggest bank have made an app where you sign up with your bank account and payment card. Then you can transfer money between friends (sending, asking and splitting). And it only requires you to login with a PIN code, and then you just use peoples mobile nr.There's obviously limits on how much can be transferred, but it's ideal for those small purchases.It's available on iOS, Android and even Windows Phone.
Link to Android version: https://play.google.com/store/apps/details?id=dk.danskebank....Currently free to use, but in some years there's a minor percentage fee.