[Billmonk][1] definitely. It sends emails whenever a new bill is shared among users, you can shuffle debts when many people owe money to others in the same group. It supports receiving instructions via [SMS emails][2] (SMS sent to an email address), but I'm not sure if a regular email would work though.


  [1]: https://www.billmonk.com/
  [2]: https://www.billmonk.com/about/sms