Share your experience!
Check the XDA Forum, also you can contact Sony regarding this
http://support.sonymobile.com/global-en/contactUs/
if you are concern about radiation, have you considered using headphones instead?
You can use the loud speaker, could you share the link to the app you want to install, I want to look more into it.
The app has a guide on how to install it w/o root access. Also this won't make much difference but you could use the loud speaker to know if someone pick up the phone or not.
The loud speaker it's quite loud, try this
place a call > tap on loud speaker > turn the volume all the way up