Not sure if it's going to fit your purpose, but I have an
ArmPod. I race downhill mountain bikes, and I've worn this through some very rough and bumpy downhill trails (and jumps) and it never has come out. Fits my Bionic with extended battery perfectly. It's a bit difficult to get the extra protective neoprene cover on one-handed, but it can be done. I like the fact that the phone is getting a bunch of shock absorption from my body, and not hard-connected to my bike. It's better to have it connected to my headphones when it's on my arm as well. The downside - I don't get a "cockpit view" of the phone. I bought mine from REI so you can likely find them around and give it a hands-on try before you buy, either at an REI or other retailer.