What we need is the next text. I'd like to nominate the bat signal.
Every time Lt. Gordon shined that sucker in the sky - and it's a lucky thing Gotham had cloudy nighttime weather - Batman would show in minutes.
I call that proof of concept.
When you're born, besides diaper rash and a Social Security number, every baby should get their own sky symbol to be used later in life on their individualized signals.
Not only would it bring people to you when you want them, it would stimulate the economy by providing work to thousands of designers and graphic artists. Copywriters would get work out of it too, because we all know eventually advertising agencies would find a way to convince people to sell space on their signals for headlines and marketing messages.
Bat ching!
The other thing is the sky is a much bigger screen than even the iPhone 6 Plus. A summoning signal can't help but get noticed, if not by the person it's intended for, at least by someone who knows them.
Then they could send a text and tell them to look up.