The office is being refurbished, so before the Christmas break I took down my shower room door monitor and used my spark core (with relay board) to do a very quick hack and remote control the Christmas tree lights from my phone. Just cut the (low voltage) cables, strip the ends and attach to the screw terminals on the relays. The lights can then be controlled from the tinker app.
Disclaimer: Although the relay board is rated for mains voltage this is only US mains voltage which is half the voltage we use in Europe. Mains power is dangerous so don’t mess with it unless you know what you’re doing. These tree lights are low voltage LEDs so this isn’t a problem but don’t go hacking any high voltage incandescent lights.
When the decorations come down I’m planning a new improved door monitor inspired by this project.