alt Hacker NewsAndroid isn't a real-time OS, but System.Nanotime() works just as well with the built-in timer as an external oscillator.
I suspect they're grabbing a digital input state change interrupt to get some real time processing, if you could get Android to give you access to a timer ISR that would work just as well.
The clicker-type computers that rely on a human input don't need anywhere near the level of precision of hardware interrupts. A software-polled button will be just fine. But even if you did need the interrupts' precision, you can do it on any cheap wireless-enabled microcontroller and then transmit to an app on an unmodified off-the-shelf phone.
This is bullshit and designed to make their devices more advanced that the outdated junk they really are. I also have doubts they work, because if they did it would be in their best interest to keep quiet and not encourage casinos to deploy countermeasures.