Richard,
Communicating through this media is not optimal. We all assume things. I never use my primary phone as my meter display. Pre-paid phones are so darn inexpensive. And no, the phones do not have to be rooted or even activated to any carrier. I get mine easily for $20 or less (in the USA). So, my phone CAN always be with my meter. But every solution depends on detailed requirements and then how much money/time/effort it takes.

Best wishes for you to find your solution. —- Duane