Install mp3 player and connect speaker to headphone jack.

opkg update
opkg install python-curl
opkg install madplay
nano /mnt/sda1/mp3.py
#!/usr/bin/python
import urllib
import pycurl
import os
import sys
from subprocess import call
import  string
#print sys.argv
url='http://tts-api.com/tts.mp3?q='+urllib.quote(sys.argv[1])
filename='/mnt/sda1/test.mp3'
#print "==> Downloading File: ",filename," URL: ",url
fp = open(filename, "wb")
curl = pycurl.Curl()
curl.setopt(pycurl.FOLLOWLOCATION, 1)
curl.setopt(pycurl.URL, url)
curl.setopt(pycurl.WRITEDATA, fp)
curl.perform()
curl.close()
fp.close()
call(["/usr/bin/madplay", "/mnt/sda1/test.mp3"])
chmod 755  /mnt/sda1/mp3.py
/mnt/sda1/mp3.py  "hello world"

ATmega32u4 code:

#include <Process.h>
void setup() {
 Bridge.begin();  // Initialize Bridge
}
void loop() {
 Process p;              
 p.begin("/mnt/sda1/mp3.py");      
 p.addParameter("hello world"); 
 p.run();
 delay(50000); 
}