So you would like to wear your smartphone on your wrist for fitness and other activities. The Wrist Rack has you covered. It lets you use your iPhone while exercising, filming, or playing games outdoors. You can swivel it around your arm and view it horizontally. Users also have the option to quickly slide their phone out.
Wrist Rack is available in 3 sizes with adjustable straps. It even has pouches for your credit cards. You can use it to hold iPhones and various Samsung Galaxy models.[Source]