I wonder why someone would be willing to lose the benefit of being listed on the Play store just to accept Bitcoin in their app, especially if they were converting to fiat at the end of the day anyway and had no intention of actually holding any Bitcoin.
edit: Although your mention of gambling or adult apps makes sense. You already lose the benefits of distributing on the Play store with those apps anyway, so why not go ahead and accept Bitcoin?
That's the primary market we expected would benefit from accepting bitcoin through an android device, and that's playing out in the developers that are using it. People will acquire bitcoin to gamble, or acquire services that aren't available through the google play store. Even using credit card details for payment exposes you to significant risk (the honey-pot issue), and this reduces that significantly. And that's assuming you'll even get a credit card company to allow you to run this type of a business anyway.
But, I'd be willing to bet that all of the alternative Android marketplaces combined (including Amazon) don't come close to Google Play in terms of the number of devices who have that marketplace installed or the number of users who look there when they want to install an app.
My suggestion, if I was asked, would be to create a google play 'free' version of the app, with a link to the bitcoin version that would allow you to play with 'real money'. But I'm not a game developer, so perhaps I'm a little naive in this regard.
It also needs to be pointed out that the technology we've developed in the toolkit is identical to what is used for an NFC push. If you are looking to create an android app that asks for payment from your android device to another android device that has a wallet, the toolkit can be used for that purpose too. It will then validate the payment. No central server infrastructure required.