Originally Posted by John_V

I didn't mean to imply that you didn't know what you were doing with your phone. I posted it because you weren't very clear as to how you were using your phone. The post may also help others that may not be as astute on using a phone as a cycling computer as you already seem to be. However,

(1) There are phone cases that will hold a phone with a protection case or slim battery case. I use one that I got from AltGear.com called a Zixtro Flash. It's not waterproof but it does do a damn good job of keeping out the rain. I've had the same phone case for three years and it's mounted on my aero bars against the handlebar and I've never had my phone get wet in the rain.
(2) Not sure why your phone screen needs to be active. I use a RFLKT to connect to my phone and I get all my ride stats across several customized screens. My phone sits horizontally on the aero bars with the screen facing up. I don't know where you live, but I live in Florida, and the sun hits the screen for my entire ride. Not once have I had it overheat or shut down while riding.

I hope you find the solution that you are looking for.