I can give you a general view about what you have to do,
First of all, you have to receive data from your coin device. Therefore you have to talk to a hardware specialist who can change this event to data, maybe using a USB cable communication or a BlueTooth or Wifi connection.
Then you can received this event data from Android OS and use it on your device. You may also require to use NDK and some C development.
I hope it helps 🙂
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solved Android app that connects to a coin collector