I think the Street Complete approach is much more practical than anything voice based: slightly gamified "quest" based entry which lets you tackle an area or a data type in detail.

It's pretty much impossible to do any meaningful and accurate data entry while riding a bike, whether the interface is touch, voice or whatever. You need to be able to verify that the phone has accurately captured what you were trying to tell it, not just take it on faith that it's worked, and that means looking at the screen carefully. Good luck to them making this work reliably.