Finding a bike mount for a phone is very easy, finding a decent bike mount is a whole other story. What I was looking for was a way, to get my OnePlus 3 and my Xiaomi Yi 4k securely onto my handlebar, without needing too much space, since my handlebar was already pretty packed.
The moment I stumbled over the QuadLock, I was amazed. It looks very simple, yet secure, and from my experience with it, it accomplishes exactly that. They offer two different bike mounts, the normal bike mount and the Out Front mount, which is the one that you can mount their GoPro mount to, a car mount, a tripod mount, a sports armband, an adhesive mount for flat surfaces, and a belt clip, so you can mount your phone to pretty much everything.
Finding a fitting case was the biggest hurdle. QuadLock themselves only sells iPhone cases, and the Universal adapter. The universal adapter requires a hard plastic case though and explicitly does not work with TPU cases, so the beautiful TPU case I had before had to be replaced. After searching for a long time and writing with the QuadLock support, which is very nice and helpful by the way, I found a case, that worked with the adapter, the Orzly FusionBumper.
As you may notice, with the mount itself, the GoPro adapter, the Universal adapter for the phone, and the case, you have to buy a lot more that with your usual bike mount, which is a single 15$ item. This only got worse, once I had realised, that the GoPro Adapter was not enough and I had to buy a short extension, since the cables for the brakes and the gear changer where exactly where the camera should fit.
Adding all of that together, because the stuff was a bit more expensive in Germany, this package has cost me 106€, or about 117$. This is way more than what I wanted to pay, but it works great. It's just so easy to use, and it is way better than any of the cheap mounts that I have used before. I also have a GoPro mount, which would not have fitted anywhere on my handlebar. So in total, I think it is worth it, if you use it regularly.
Should you also have a Yi 4k and want a case, the one you can see here is the First2savvv XM2-TL-01, which looks kinda sketchy, but it is actually a really nice and well built case. Also, should you be interested in an action cam, I highly recommend you to take a look at the Yi 4k that I already mentioned a few times, I think this video wraps it up rather good, calling it a GoPro Killer.