Don't scream for ice cream; pick up your smartphone instead.

Uber, the San Francisco startup known for letting people order private drivers in sleek black cars using a smartphone app, is offering an ice cream-on-demand service — for one day only — in more than three dozen cities around the world, including Detroit.

Friday's stunt, an expansion of last year's ice cream promotion, comes in the midst of a heat wave in Detroit and elsewhere. Last year, people in seven U.S. and Canadian cities could use the Uber app to summon an ice cream truck hired by Uber to their location, provided they purchased a minimum number of treats. But demand exceeded supply, and not everyone who wanted ice cream got it.

"In San Francisco last year, we had so much demand that in order for everyone to get ice cream, we would have had to have 1,000 trucks on the road," Uber CEO Travis Kalanick said. "That's a city with 1,500 cabs."

On normal days, Uber lets people order a ride in a taxi, a regular car, a high-end sedan or an SUV using its smartphone app, after they register for the service with their credit card information.

Kalanick co-founded Uber in 2009. He said it is "a magical experience" to be able to push a button and summon an ice cream truck — or in the case of Italian cities, a gelato truck.

People will have to order more than one cone to have a truck come to them. The trucks will be out from 11 a.m. to 5 p.m. local time. In Detroit, ice cream will serve five people for $20.

To learn more, download the app or visit Uber's blog here.