You don't need a USB cable, that's to keep the phone charged. I've got this hooked up to my Razer 2 so I can check temps easily. You do have to pay $1.49 to unlock the dashboard with the pretty graphs, but it's worth the money.
I'm looking at this in the google play store and it lists possible "in app purchases" as up to $28... can you confirm that you were able to get "pretty graphs" for under $2? Any idea what the $28 purchase would be?
edit: While I'm at it... how was the purchase done? The only paid android products I've purchased had a purchase option directly on the play store so it was easy enough for me to input my CC info just for that one purchase... how does that work for in-app purchases?
In app purchases are done through google play. Just triggered from in the application, a SKU is passed to the google sdk and google takes over everything else. As a developer I'd never have access to your actual credit card info etc.
Any attempt to use a non-google play store integration for purchase handling can result in a ban and more, not of just the application but of the whole developer account etc.
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