I think that if you need the product to increase the amount of workable hours in a day, you're doing something wrong to begin with. The idea of Polyphasic sleep in itself is interesting, but do it for the right reasons (more time to communicate with friends/family who are in a different timezone, work nightshifts etc.).
One other thing to consider is the fact that sleeping less means you've got more time to spend, also during hours when almost nobody else is awake. For some this isn't an issue, but for others this could prove to be difficult. I for one would opt for an Everyman cycle, since it allows you to be awake during relatively "normal" hours.
Besides the fact that a direct debit payment is reversible, isn't there also a timeout between the authorization and actual debit (in The Netherlands, I believe it's about 1-2 days)?
How do they handle chargebacks/failed payments and do they charge their merchants for failed payments/chargebacks?
I think direct debit could be huge on mobile, but given the fact that every direct debit payment can be cancelled within a month or so, how do you reduce your risks?