So.. to spell it out completely, here's how to skip one track (assuming no menu is active on the display):

echo 'BUTTON=0x0020DF11' > /proc/empeg_notify

Or like this:

## press/hold the NextTrack button:
echo 'BUTTONRAW=0x0020DF11' > /proc/empeg_notify
## delay for, say, 1/4 second
..
## Now release release the NextTrack button:
echo 'BUTTONRAW=0x0020DF11.R' > /proc/empeg_notify

Personally, I prefer using names rather than numbers:

## press/hold the NextTrack button:
echo 'BUTTONRAW=NextTrack' > /proc/empeg_notify
## delay for, say, 1/4 second
..
## Now release release the NextTrack button:
echo 'BUTTONRAW=NextTrack.R' > /proc/empeg_notify