(CBS) – Only days since its launch, one app is being called a cultural phenomenon.

The Pokemon Go app is crashing servers due to demand and cashing in — to the tune of billions in stock value.

But as CBS 2’s Jeremy Ross reports, it is also drawing some concerns.

It’s the meshing of GPS and cell phone cameras, overlaying a digital domain to battle virtual monsters, called Pokemon, and collect them for players’ arsenals.

Player Rex Lee, 31, says Millennium Park is crawling with Pokemon for the capturing, as well as some bonuses for users.

“There’s a lot of stops, designated points and landmarks in Millennium Parks,” Lee tells WBBM Newsradio. “They incentivize you to come visit it because you get items that you can use in the game when you come near it.”

There are fears cars could collide with gamers on the go, or add to distracted driving.

Tamara Kaldor of the Erikson Institute Tec Center warns parents about the potential dangers.

That includes a Missouri case in which police say thieves waited at a Pokemon site to pull off an ambush-style armed robbery. No word from Chicago police if there have been any incidents here.

On the positive side, Kaldor says players stand to get a lot of exercise.

The start-up screen for the app warns players to be alert at all times and stay aware of their surroundings.