How do you play scary noises in your friend’s house at 3 am from anywhere in the world? Let me enlighten you.
First off, they’ll need a quality home speaker system. The "Sonos" speaker system should do nicely. It uses home WiFi to send and receive control signals. Secondly, you’ll need some basic familiarity with Python.
Someone conveniently took the time to analyze packets sent and received by the Sonos system and created a Python library called SoCo, which lets you craft your own packets to send to the system: SoCo
So with this library, you can get device info (is it in the living room or dining room?), change the volume, and even feed it an external URL to stream from... This really opens up the possibilities for scary noises like moans and screams. Get creative with it.
Now just write a simple script to utilize the SoCo library and play pre-loaded URLs, like the script linked below:
The real trick is being able to use this script from anywhere. For this, access your victim's home router (i.e. while on their home network, type in your default gateway IP into the address bar of your browser). The default login for home routers is often 'admin' : 'admin'. Change the router settings so you (1) have forwarding from the WLAN to the IP of the Sonos on their local network, and (2) have a static DNS service so you always have an access point to their home network (since IPs may change). Do some Googling if you don't know what I'm talking about, but this will allow you to access the Sonos from the public-facing IP of your victim’s home network.
One more thing, don’t ever do this to your poor old auntie. That’s just evil.