I have tried using my phone but battery like was not very good on the phone battery alone, yes I have an external source also but not worth it and the phone does get hot.
I find it easier to just use my Garmin and forget about it.
I have used my phone on long trips with external power to transmit my location for family using programs like Glympse or Instant Mapper they can see data from computer or their phone on a map to track me live, phone is in saddle bag so I'm not using it for my feedback.