i tried using Daily Roads Voyager on my old Droid4 a while back, and even sent the developer a few bug reports and tried beta versions for him - the dev was a very responsive person. that said, my main complaint was that the camera's viewing angle was very narrow compared to a real dashcam, and that's something no app can fix. also, at speeds anywhere above 10 mph, there was a very annoying rattling/buzzing in the video caused by the phone mount. and i was even using the official motorola car mount for my phone, not just a cheap generic. at highway speeds, the video started getting shaky and vibrated a lot, making it blurry. the camera would chase focus till the app added a setting to lock focus at infinity, but it was still shaky.
the other issue was that if i wanted to use my phone for playing music (whether streaming or from SD card), or navigating w/ google maps while it was also recording, the phone got VERY hot. and if a phone call came in while it was recording, it stopped recording and wouldn't resume on its own.
i guess if you had an old phone you could dedicate to being a dashcam, and had a way to mount it so it was hidden and unlikely to be stolen... and then had a way to make it automatically start and stop w/ the car (or even better, work in parking mode), it would be fine, but if it's the phone you use daily, it's finnicky. for me, it was worth the small investment in a real dashcam. plus, that's an awful big battery to keep in the heat of the car every day.