I wanted to use a Kardia ECG monitor which needs a smart phone app. Kardia has an extensive list of compatible phones but no mention of Fairphone. [Kardia is a US product - so no surprise there given low penetration I think.]
The good news is that the AliveCorKardiamobile 1 lead monitor I have now bought seems fully compatible with my FP5.
Why wouldn’t it be? The communication between the measuring device and the phone is by ultrasound - so an area for incompatibility I guess. As for the rest it seems plausible to me it’s just bog standard Android processing.
Hope this is helpful to other FP users.