I have been using two systems. A soft case for an Iphone that straps to the forearm. I have added a strip of velcro loops to the back of the case and a strip of the hooks to the forearm of a jacket. It does a fairly good job of keeping the Iphone in place. Downside the softcase is not waterproof so the phone needs to be in a lifeproof case. If to warm for the jacket then I use the lifeproof strap on the upper arm. Downside, I have to detach the Iphone for anything more than a quick look. But if twists off fairly easily and with the magnet attaches pretty quick and secure, even if the lever lock is not engaged, but I use an old Iphone with the setup.