Don't throw away those old phones - they work just fine for a variety of tasks.
One of my other hobbies is star-gazing. I have a small motorised scope, but also used to have a larger scope, which was completely reliant on muscle power (it has since gone to a friend).
When I found myself with a spare old Android phone, it quickly got fixed to the tube of the telescope and loaded with software that let it act as a kind of finder for the scope. You'd type in what you wanted to see, and arrows would appear on screen, telling you which way to push the thing. It took some setting up, to get it accurate, but because it was securely fixed in place, I only had to do this once (and then fine tune it, occasionally). Great fun.
