Listen Audiobook Player Intents 

Use the "Service" target type with the corresponding intent string. 

Extra option example: speed:1.5

Description Intent String Extra option
Toggle play/pause com.acmeandroid.listen.action.PLAY_TOGGLE  
Play com.acmeandroid.listen.action.PLAY  search:Invisible Man
Pause com.acmeandroid.listen.action.PAUSE  
Short skip back com.acmeandroid.listen.action.SKIP_BACK_SHORT  
Short skip forward com.acmeandroid.listen.action.SKIP_FORWARD_SHORT  
Long skip back com.acmeandroid.listen.action.SKIP_BACK_LONG  
Long skip forward com.acmeandroid.listen.action.SKIP_FORWARD_LONG  
Previous chapter com.acmeandroid.listen.action.SKIP_BACK_CHAPTER  
Next chapter com.acmeandroid.listen.action.SKIP_FORWARD_CHAPTER  
Open the app com.acmeandroid.listen.action.OPEN  
Exit the app com.acmeandroid.listen.action.EXIT  
Create a bookmark com.acmeandroid.listen.action.BOOKMARK  
Skip to next bookmark after current position. com.acmeandroid.listen.action.BOOKMARK_NEXT  
Skip to closest bookmark before current position. com.acmeandroid.listen.action.BOOKMARK_PREVIOUS  
Change to previously played book. com.acmeandroid.listen.action.BOOK_PREVIOUS  
Decrease volume com.acmeandroid.listen.action.VOLUME_DOWN  
Increase volume com.acmeandroid.listen.action.VOLUME_UP  
Set volume level com.acmeandroid.listen.action.VOLUME_SET "volume" (value between 0 and 8)
Decrease playback speed com.acmeandroid.listen.action.SPEED_DOWN  
Increase playback speed com.acmeandroid.listen.action.SPEED_UP  
Set playback speed com.acmeandroid.listen.action.SPEED_SET "speed" (value between .25 and 5)