The ram mount, I have that now on my Ribelle, but a nice pothole or sharp bump will jar the phone loose, it's happened to me twice now. First time fortunately was right before a set of train tracks, and train was there so when I noticed it missing, i was able to circle back and use my Cardo to relocate where it fell off. Second time, it was on a shitty stretch of road, I hit some flat potholes and it jarred out of its holder again, but thankfully I seen it and it was on my tank and I was able to grab it and pull over and re mount it before it hit the pavement.
Even with those though, they want an actual tether, something hard mounted/tied on/bolted on. If you come off the bike don't need the phone flying somewhere and then trying to find it, or it gets ran over or causes other issues when it smacks someone during it's short but fast flight.
Aaron