I was just reading about the $100 home made Muon detector built by some engineers at MIT in the link below:

http://news.mit.edu/2017/handheld-muon-detector-1121

It got me thinking about the use of muon tomography to find unknown cave passage.

I'm not an expert in particle physics or geophysics, so is it feasible? Would the accuracy of a home made device be enough to give reliable data?

Sounds like a good idea for a BCRA paper.

Thoughts?

See https://www.nature.com/articles/doi:10.1038/nature24647.  You should get passed onto a download of the pre publication paper.  Good luck, I think you will need it.  It might just work for somewhere like Malham Cove where the chamber might be 'above your side' but not for chambers 'beneath your feet'.  But I fear the development work will be significant / nigh impossible.  Still something for CREG to think about.

Some Hungarians had a go some years ago around Budapest: https://indico.cern.ch/event/163821/contributions/1415035/attachments/195027/273564/LaszloOlahZWS11.pdf

and the 17th International Congress  of Speleology in Australia this year had a paper entitled "Cavity searching and 3D density mapping via muon tomography" by some of the same people (Gergely Sur?nyi, G?bor Moln?r, Gergely G?bor Barnaf?ldi, Gerg? Hamar, L?szl? Ol?h, Dezs?Varga)...