I have a Samsung S5, and ride the bike to and from work daily. I just installed a Rokform stem mounted kit and case on my road bike stem, and rode to work with my beloved S5 firmly attached to the stem mount this morning. All is well, so far, as I experienced Strava talking to me throughout the ride about how I was doing! Times on segments were announced real time, as the prior 6,000 miles Strava was buried in my seat pack with my phone set to SILENT.
This stem mounted kit seems very solid, in every way. It is secured by the case for the phone, two magnets, and a lanyard wrapped around the stem, just in case. I'll check back in a few weeks once I have some miles on the case and mount.