I had a bag like the one linked to. The issue I had was my iPhone 5 mounted in an Otterbox case and with it inside the plastic the phone would overheat on hot days. So I took the holster that comes with the Otterbox Defender case and zip tied it to the stem. Works perfect and makes it very handy to get it on and off the bike.

I have a Wahoo speed and cadence sensor along with a Wahoo heart rate monitor connected to my phone. I use the Wahoo fitness app which is free and then upload from within the app to Strava. I use an external battery pack that is placed in a top tube bag to power my phone. I was going to get a Wahoo Rflkt but with it being so buggy I went with the external battery pack plus I can use it off the bike when I need it.