  We study cosmological applications of the holographic energy density.
Considering the holographic energy density as a dynamical cosmological
constant, we need the Brans-Dicke theory as a dynamical framework instead of
general relativity. In this case we use the Bianchi identity as a consistency
relation to obtain physical solutions. It is shown that the future event
horizon as the IR cutoff provides the dark energy in the Brans-Dicke theory.
Furthermore the role of the Brans-Dicke scalar is clarified in the dark
energy-dominated universe by calculating its equation of state.
