[Splines]

You can get it to recognize fingerprints or a short version of your password if it's even been fully unlocked for the current phone session. It's a little fiddly and may not meet the level of security you're looking for, but it's an option.

[GordonS]

I knew about the short password, but hadn't seen the fingerprint option - that's just what I need to make it "secure enough" while being usable!