[belese]

Your code look strange :

PHP Code:

while(1): #Do this in order to know when video isn't playing
        if xbmc.Player().isPlayingVideo():
                VIDEO = 1
 
        else:
                VIDEO = 0 


will never go out, and put a sleep somewhere,
something like :

PHP Code:

while not xbmc.abortRequested():
     time.sleep(1) 


and why call python function with os.system,
it' python in python so call the python function directly, and import your files.

and do a print somewhere at the beginning to see if service is started, it'll appear in xbmc.log

and instead of use ps, you can take a look here :
https://github.com/xbianonpi/xbian-config-bash/wiki/Services
but you have to update xbian config if you are on alpha4

and a python wrapper for xbian-config is done here :
https://github.com/xbianonpi/xbian-config-python/blob/master/resources/lib/xbianconfig.py

---

Read a bit more you code,
but i think you can't override player like you do to do this,
if you override player like this, it will react only if you call your player from your script
but maybe i'm wrong, need to be tested.

eidt : no, sure i'm wrong, it should work also.

here's a basic code (not tested at all)

PHP Code:

import threading,time

waitvideostop = threading.Event()

def startDL() :
   #do some stuff here

def stopDL() :
   #do some other stuff here
   waitvideostop.set()


while not xbmc.abortRequested():
     if xbmc.isPlayingVideo():
           myplayer = xbmc.Player()
           myplayer.onPlayBackStarted = stopDl
           myplayer.onPlayBackEnded = startDl
           waitvideostop.clear()
           waitvideostop.wait()
    else :
          time.sleep(1) 


and onPlayBackEnded is called when you do pause (in Eden, don't test in frodo), so perhaps you have to check is player is not in pause before restarting all dl