There is a much easier way to get recalcitrant teenagers out of their warm bed in the morning. Buy a couple of bags of glass marbles and put them in the freezer.
Warn your teen that you will only call them X number of times (two is the most I would give) before you take unpleasant action against them.
When the teen does not get out of bed, get the frosty marbles, open the bag, pull the covers up just a little, and pour the marbles into the bed with the teen.
When those icy cold marbles hit that nice warm rear end, you will be treated to the sight of a teenager levitating out of the bed!! Only rarely is a repeat performance necessary.
As a side note, this doesn't get the bed wet, either!