I think you SHOULD use MD5 for hashing of non-secure things. I say this because MD5 is KNOWN to be insecure. My fear would be that some early adopter would start using Blake in a (semi-)secure fashion before it was a standard: Blake gets ignored and something even better comes out. And software being what it is, since Blake isn't specifically called out as no longer be secure by NIST, it just sits in the code base forever because it's forgotten. On the other hand if someone sees MD5 in the security layer and they KNOW that there's a better solution that's a standard, it will likely be updated.

can you provide a source about the storage of your fingerprint data on the phone?

our software is installed there and we constantly have to go on the server to do updates or make other changes or diagnose issues

What have you tried? Where are you getting stuck? Essentially you are just asking us to do the work for you.