Google has removed this application from the Play Store due to the way the app uses SELinux permissive mode that allowed the app to record inline audio. Maybe if the Android dev team bothered to make a worthwhile screen recorder with working inline audio other people would not have to find workarounds in order to get a working implementation.
Since the app has been pulled and it was a paid app, it is no longer available even to those paying customers on the Play Store, meaning Google has taken away a rightfully paid app they had no issue months ago carrying. Luckily the dev is a stand up guy and has offered the paid version for free on his XDA page in order to make up for the shortsightedness of Google.
The only audio recording Rec. has is to use the external microphone, which will record any sound outside of the device and is no good for noisy situations.
Features such as audio recording from the mic automatically mix into the screencast videos (extremely useful for tutorials) and also pausing and resuming screen recording,