A couple of my IoT students are planning on designing and building a flow to control a strip of RGB lights on a Christmas tree (using a distance-value from an ultrasonic distance measuring device HC-SR05).
Here's a very rough sketch of the ideas discussed during their first session.
They discussed the idea of changing the colour of the RGB strip as you walk nearer to the tree or changing the brightness of a single colour. Maybe if they have enough time I'll encouage them to do both!!
This might be the first Christmas tree that has two IP addresses (ho.ho.ho. merry & ho.ho.ho. christmas ).