Do you want something that switches according to a frequency being higher or lower than the threshold or being a particular frequency?
For a specific frequency, my first thought is a PLL (NE556 for example) with lock detect controlling the power switch. If a high/low frequency determination is needed you either have to use a rather complicated digital filter or a fairly trivial software routine to measure the frequency, either way you need an ASIC or an MCU. There is no single component that can both do the measuring and switch the power but it should be possible to do it with only a few discrete components.
Brian.