Used to use a Garmin Zumo. I'd use it most (1/2 - 2/3rds) of the time; Even if I knew the way, as it would mean I'd worry less about going past my turning, and focus on the road instead. I'd use it without audio, so I'd glance down to see how far to the next junction, and then not look it again until I was near. The distraction was no more than it took to check my speed - so quite safe, and I never had a "moment" with it, although there were a few occasions where, needing to keep my eyes on the road, I went past the turning. Later I paired it to my earphones, to get audio instructions as well, thinking this would help. But I couldn't get it work reliably - the audio would come and go (I think it was fighting with my phone for access to the earphones). On one occasion it went silent for over an hour and poured out all the instructions it had saved up in a continuous stream for about 5 minutes. Not great. The other thing that was irritating was when you had to modify a route in the middle of a ride - the only safe way was to stop for 5 minutes and poke the nav into submission until it showed the new route. I've now got rid of it, and instead I'm going to use my phone in a holder attached to the bars. Google maps or waze probably (I like the way you can send a route directly from google maps to your phone - a whole lot easier than with a sat nav). Bluetooth between the phone and earphones will be reliable without any other devices trying to get their oar in, and I can use voice instructions to get the phone to do what I want ("Hey Google, stop the music"). I've not yet tried it out on the bike for real, but I'm hoping for solution where I don't have to look at the screen unless I really want to, and where I can get the machine to do what I want without having to stop, get off and reprogram it. Never had a close call from using a sat nav. Close calls due to other distractions? Oh yes, far too many. I once ran my car clean off the road, into a wood, and totalled it against a tree, all because I saw something in the valley that looked just a bit different from usual.