Single mobile app subscription model for multiple platforms

If I have an iPhone app, Android app, and Blackberry app, is there any way to implement a monthly or yearly subscription-based billing scheme such that a user need only pay for one subscription in order to use my app on any device? The problem is that each app store seems to have the stipulation that any fees required to use the app must be paid through them so they can take their cut.

Dropbox does this, but I think they can get away with it because their apps will work for free, and the subcription only offers more storage space. Is their any way to do this type of billing for an app which requires a subscription in order to be used at all? If not, will simply adding some sort of free functionality get me around this?

Thanks.

[EDIT]

Let me be clear, my question is about how this can be done legally. I'm basically running up into the same issue that caused the Financial Times to stop offering its paper through a native iPhone app. The difference betwe开发者_StackOverflow社区en them and me, though, is that I don't mind paying the app markets their cut. I just want to know if this is possible; a user can either order their subscription through Android Market or the App Store, and if a user isn't paying through both stores then I think I'm violating the terms of one of the stores.

You could try Bango.But you need to implement a possibility to transfer the Bango User IDs between your different apps on the different devices. They offer a service where they bill a recurring fee to the user. They offer a SOAP-Based API (amongst others) you can use from your app.

But beware: there are some legal restrictions concerning inapp payment in the Apple AppStore and the Android Market and maybe also in the Blackberry AppWorld.