Most tv's have power button memory, if your watching tv and the hydro goes out, then when the hydro comes back on the tv will auto turn on because that's the last state the device was in.
To test this in a tv store simply unplug the tv while it's turned on, if the tv turns on again once you plug it in (without touching the power button) then that's the tv you want. Samsung, sony, insignia, RCA, most pc monitors, all do it.