Ever wanted to collect data from your Arduino and analyse it?
You can download an add on for Excel here . It’s from Parallax and allows you to send data via a Com Port and it will be collected.
So I’ve done this with my fish tank (a constant 23 celsius today give or take) and a light sensor. It gets darker as the sun goes down
So many ideas. You can link several sensors to it so all you need to do is think of the data you want to collect.