Wouldn't work, you'd be dead seconds after combat ended and it wasn't turn based any more.
Edit: To clarify the damage would probably tick off to fast in real time to be able to out heal.
True. You could either have it only activate during combat because magic, or make it an activatable item. Or it only activates after you get attacked, and stays active for like 10 rounds, refreshing the timer every time you get attacked.
