From a Mac perspective, this is no different than capturing video from an analog or digital source.
Depending on the output of the Android Tablet, you can use an analog capture device or a digital (HDMI/DisplayPort) capture device. That interace will allow you to input the video to your Mac. You'll also need capture software (these devices come with it). I have used both and currently use the HD60S for capturing output from all sorts of devices like laptops, iPads/iPhones, an XBox (not much) and a DVD/VHS player for trans-coding old movies.
The critical part comes down to your Android tablet and what video adapters it supports. Basically you need an adapter like the Lightning to Digital AV Adapter that allows you to connect an iPad/iPhone to a screen or projector but one made for Android - an Android to HDMI adapter. Unfortunately, that's not something I can recommend as Android isn't very much discussed here (and I personally avoid Android like the plague - my experience is limited here).
However, you connect that adapter into the video capture device described above, and you can record game play to your hearts content.