Wake up an agent

Is there some way to get started (wake up) a machine with an agent in case when the agent is suited for a build (registered, enabled, but disconnected, because the machine is down)?

I mean something very similiar as it is done in a plugin for vmware, but simply to wake up a computer instead of starting a virtual machine which hosts an agent (and maybe be able to shutdown a machine after some time of inactivity to have it like in other cloud versions).

I have plenty older machines which can serve as agents, but I do not want to have running 4 machines 24x7, if the builds typically run only 2-3 hours per day per machine, but many times simultanoeusly.

My TC server runs on a linux machine, it is not problem to run some kind of wake on lan software there, I can wake up any agent machine manually, but I would like to have it incorporated completely within TC (not only triggered by a developer/Personal builds). VMWARE plugin seems to be very good example, it looks that very little must be changed in the code of this plugin to achieve my goal.

Jaroslav