This tutorial will show you how to run a simple mobile-friendly website from your Raspberry Pi that will allow you to remotely wake up your power-hungry computer, so you can remotely access it.
When you’re done, just put it back to sleep from within the remote desktop service (or use the mobile app plus a small background server running on your desktop to put it back to sleep – this is described in the instructions).
The app pings the computer from the Raspberry Pi to inform you of when the computer has woken up and established network connectivity.