Not really.

Quoting GP: I think a good balance between security and usability would be to allow fingerprint or iris scan when the phone has been constantly in my proximity but require a pin (password) if the phone is taken away. The proximity could be determined for example by pairing the phone with smart watch.

When combined with a fingerprint sensor, smart lock keeps the device completely unlocked while "triggered" (by being on-body, or close to a trusted BT device, etc), and the fingerprint unlocks it while not triggered. It doesn't ever escalate to requiring the pin/password/pattern. Please correct me if I'm wrong, because I'd like to be.

My solution is to use the "Screen off and Lock" app[1]. It acts as a local Device Administrator to be able to force a password unlock. I added the widget to my home-screen where I can actually lock my phone if needed (leaving it somewhere for a period), and I can use the fingerprint the rest of the time.

Definitely not a perfect system. I wish that I could set timeouts and map the power button to do an admin lock. Also, having to use a 3rd party app for this is quite likely its own threat vector.

[1] https://play.google.com/store/apps/details?id=com.katecca.sc...

Yeah, the Smart Lock functionality doesn't really support configuring your own primary-vs-fallback behavior.

I'd love to have features where the fingerprint is only good enough under certain circumstances, such when the phone hasn't been idle for too long, or when combined with an RFID tag.

You are correct, it's not a perfect system or perfect solution. No security system is perfect.

You're not wrong. I use smart lock and fingerprint on my 5x. I actually would prefer it to require fingerprint when near my watch with password fallback, and require fingerprint+password when away from my watch, but that isn't currently a possible configuration as far as I can tell.