As android generally reserves direct audio access permission to system processes acting as delegates for applications through Android app-only APIs, a stagefright executable would not be something you could add to a secured device if it was not placed there by the system vendor. However, you can accomplish your need to play audio upon request from the adb command line by using an Intent.
Here's an example - adjust to your specifics:
am start -a android.intent.action.VIEW -d file:///mnt/sdcard/ringtones/hangouts_video_call.ogg -t audio/ogg
Remember to change that to audio/mp3 if that is your file type
This utilizes the default player - if doesn't give precisely the behavior you want, you may need to make your own custom player app with that behavior, and then use an Intent (with an explicit package name) to trigger it from the command line.