Exactly what it would happens to baby got its umbilical cord wrapped around the neck and choke off as in layman term. Would you want to deprive yourself oxygen for your brain during sleep if wire wrapped around your neck??
Even if unconscious during sleep, you could yank or unplug cord off the phone and phone dies before it wakes you up. You may be dreaming that you were trying to kill a snake by ripping its head off while actually you rip cord off the phone. Seriously.. It actually happened to me that I was trying to kill glowing red eyed monster by pulling off its neck and after a struggle that I couldn't kill it, I woke up realizing I had my RS clock w/ red LED in my face and pulling its cord connected to clock (not the plug on back) sheesh. I put it back where it belongs.. what a freakish dream!!! 
Last thing you should worry is to get a bigger battery for phone and lose the cord 
Catty
