Mobile Phone Greeting Confusion

How many of us has been on either side of this situation?

A person answers their cell phone in public and says "Hi!" The person in front of them turns around and says "Hi!" right back.

Mortifying.

What can we do to prevent this? There needs to be a way to distinguish between a greeting when you are answering your phone and a greeting when you are trying to say "Hey you! Aren't you my long lost sister that I owe $100.00?"

I thought at first one could answer with the name of the caller. "Hi, Mike!" But you don't always know who is calling and it takes a moment longer to say. Even worse, depending on your relationship with the caller, it could make the aforementioned embarrassing situation much more horrifying. Imagine walking up behind a stranger and saying this:

"Hello, sexy."

"Hi, Grandma!"

We need a greeting that is simple, generic and clearly means "I am answering my phone." In Japan, they have such a thing: "Moshi moshi." What does it mean? Who cares. It's just what you say when you answer the phone.

I am going to start answering my phone this way, so if you are a person that calls me, be warned. I am sorry to break American cultural tradition, but if it causes me to stop embarrassing old ladies when my girlfriend calls for last minute requests at the grocery store, then I am doing it.