[Skunkworks] Android streaming media question

Hi All, A quick question for android devs (and pardon my ignorance). Assuming that have streaming media (audio and video), how would you go about charging for the media so that either: a) Each complete download to device is charged, or b) The used is charged for the total amount of data used. And is it possible to block a device that has downloaded the data once from downloading it again? -- Regards Brian Ngure