I use a sonoff wifi smart switch. Something like this:
https://cdn.itead.cc/media/catalog/product/s/o/sonoff_03.jpg

You connect it to your Wi-Fi and control it with your phone. The software works on the Internet also not just on the local network. When you energise the switch, it will basically short the 2 output terminals. So what I did was make a splitter for the power on/off pins of the mainboard, connect one pair to the physical power switch of your PC case, and the other pair to the 2 output terminals of the sonoff. You'll then be able to turn on/off your PC with the physical like you would normally or with the sonoff wirelessly inside or outside of your home network