They state:

Droplet is the first app of its kind that lets you send payments completely outside of the traditional banking and credit card systems. It’s a bit like cash – but digital and mobile. You don’t need to connect your phone to your bank account to use Droplet. Instead you just top up your account via your phone, a bit like you’d draw money out of a cash point. https://dropletpay.com/about/

What does that mean? Is that a new implementation of chaumian e-cash?