In your opinion, would a voice-based contextually aware device be a big enough distraction/safety reduction to offset it's value?
Heads up is only really helful for the edge-case that is not apparent. Ie, it helps you pre-visualize something. It might be something that is like a blind-corner + turn. Or it might be a confusing intersection (5-way). Or a left hand exit, et. This would help you set-up the right way ahead of time. Rather than just telling you XYZ at the last minutre.
You need a time/distance dynamic lead-time tho, and it is this that current GPS systems suck at. The hard part is just getting the software right. It's a distraction if its not at the right-place + right time.
I've used a GPS on a bike since the mid-late 90s. To me, the use case is completely different than in a car. I'm not driving a rental from the airport to the hotel, and I'm rarely trying to find something in a major city. On a bike the GPS is a nice-to-have tool. But it is not so essential that I'll spend a lot of money, or require it to be constantly displayed on my visor.