Mine started when I was looking for a tool for demonstrations when teaching particle physics on a budget. Something that actually could do physics in this domain. The first thing I looked at was these cheap GM counters and started to think about turning them into a coincidence detector.
First I built a lead coincidence detector that detects electromagnetic cascades caused by muons at the end of 2014. You can check out this prototype here.
This time I made a cosmic ray telescope type detector. I added the camera capability to this, taking the first pictures with the detector. I shot a video about the making of this second prototype - was made all by hand on universal boards.
I received a lot of good feedback and met fantastic people. Most people wanted kits to build and understand how the parts work rather than having a ready made much more compact detector that my initial aim was.
The highlight of this programme for me was when we actually managed to capture a muon decay with this detector. You can check the post about this here. Here comes the picture we took. We had trouble with the lighting, but we managed to get this result.