What to look for in bone conduction headphones for bike voice navigation?
Point 1, hearing the outside world, is mostly easy.  If the audio is too-high a volume it can still drown out the background, but that's got to be quite loud.
Point 2, these headphones have to work with your device.  If that means bluetooth, then battery life becomes a consideration.  If your device has audio-output jack then that's another option. 
Do note - Bone conduction headphones use their internal battery all the time.  Bluetooth is additional power usage.
Generally speaking, the music fidelity of bone conduction head phones is down there with cheap AM radios.  So your point #3 is going to be hard to match.  It is certainly audible, but quality is low.   They are great for audiobooks though.
4, phone calls.  I have BC headphones that are just headphones, no microphone.  So they can beep should a call or message arrive, but I can't take the call.  There are variants that have a microphone and call control button.  If you use an audio out jack, you might need a 2.5mm 4 way TRS connector, or maybe a 3.5mm version.
Unmentioned - sweat.  Some BC headphones have a control box partway down the cable.  For me, that used to clip to the collar or the HRM strap, which worked well.  But sweat tends to get inside the controls and make them flaky, then non-functional.
Another feature, is some way to easily turn them off.  Ideally a button that you can hit without looking, that shuts off the sound should you need to focus on something else going on.
Cost is the last mention - you could spend multiple hundreds of dollars, but thats overkill for on a bike.  Something down around $50 USDish would be less upsetting when they do eventually break.