Handlebar-mounted "turn indicator" that can pair with a smartphone for turn-by-turn GPS navigation
I've had a phone in a bumper case come off the handlebars several times without damage. But my handlebar mount kept getting broken in the bike shed at work so I  switched to a top tube bag (which also holds a tube and basic tools). The low light readability is still an issue, but you're over the top of it a bit more which helps. Where I put tools you could put an extra battery. The bag is firmly attached to the bike so won't come off, and the location means it's highly unlikely to hit anything. They're cheap so it's worth a try. This way there are no worries about device/phone/app compatibility.