This app was mentioned in 2 comments, with an average of 1.50 upvotes
Spectrum Analyzer for my phone
https://play.google.com/store/apps/details?id=com.keuwl.spectrumanalyzer
and pretty much anything else keuwlsoft produce
https://play.google.com/store/apps/dev?id=6082914357148822158
No Octave on Android, but we do have this one that looks promising. I'll check it out!