There is some 2FA approach for use with P2SH as Gavin describes: https://gist.github.com/gavinandresen/5616606, but that's is likely way overkill to make it work with a micropayments subscription type of of application.
Coinbase's subscriptions service probably could provide greater ease-of-use, and since it is already offered today by Coinbase that could be implemented more easily. But the problem with Coinbase's subscriptions is that the customer is pre-authorizing the "merchant" to withdraw. With the Open MediaWallet concept as I understand it, the content creators would each be merchants and thus that Coinbase subscription model doesn't work. If there was a single Coinbase account for all MediaWallet content creators, about the only protection from abuse (e.g., payment drawn without approval by a scammer acting as content creator) comes from the amount being limited (i.e., $X per-week limit).
Rather than subscriptions, the micropayments channel (which BitcoinJ has now implemented) would be a better fit:
- http://en.bitcoin.it/wiki/Contracts#Example_7:_Rapidly-adjusted_.28micro.29payments_to_a_pre-determined_party