People have been trying to figure this out for the longest time.
Rip redbox discs down to 65% quality (no detectible loss on the screen; even on a 46" LCD) using DVD shrink and avg movie of 1hr 45 mins to 2hrs is 2.7-3GB and play the VOB's with Mx Player off your SD card the whole process will take 20 mins if you convert down to a 700mb divx you're looking at 1.5 - 2 hrs to do the conversion
Early on in the Netflix streaming there was a trick you could use to capture the streamed video and save it as a video file. This wassoon 'fixed' and Netflix has been using DRMto prevent capturing the video. It isn't like trying to copy a Youtube video. Sorry.
Amazon will should let you cache a rented movie (but I am not really sure), but it will still be DRM'd.
Or, you could just rip a DVD with the software of your choice (an old copy of DVD X Copy still works for me),and then play in the video player app of your choice. (I like Moboplayer)