PieMessage uses an AppleScript to capture iMessages as they arrive on your Mac system. A Java app scoops up those messages from the script and forwards them to a custom messaging app on an Android phone. You can reply to one-to-one messages from your Android device but currently can’t send group messages; instead you can just receive them. There are some limitations to PieMessage: You can not send images and can not see when someone is typing though the author plans to add more functionality in future updates.
Source: https://thehackernews.com/2016/05/imessage-android.html