I use the RFLKT with my Droid Turbo running 5.0.1 and it works pretty well. I have BT smart cadence sensor and a Scosche HRM. The biggest problem I had was trying to get a chest strap HRM to connect with the phone when it's in the underseat bag. Like you, didn't want to invest in a dedicated computer that does the same thing a free app does.
Roger