"Say you are at a corner store and you see a guy steal a muffin - you can just report it and all the people in your area will know that that guy stole a muffin," said participant Kory Calicat-Wayns, 17.
Facts supplied by app users will be kept in a database and appear on a map, Calicat-Wayns said. Each type of crime gets its own icon, and users can filter using the sidebar.
"What sets us apart from other sites is that we are user-friendly and mostly interactive," said participant Cameron-Javon Scott, 14.
The app aims to report small crimes that often go unreported, such as vandalism and petty theft, the students said.
"I actually live in North Philly and I see the crime daily, so I know what goes on," said Jimik Ligon, 17.
Graduate student Michael Korostelev, one of the instructors for the program, said, "Even if the police don't directly respond to these small crimes, they can see a pattern of what goes on and where, so they can maybe change the way they patrol and things like that."
The Gotcha team members are among more than 200 minority high school students who participate in Apps and Maps. They spent about four weeks creating the app, picking up programming skills along the way, Korostelev said.
He said the students get to "see what is possible" with the skills they have learned.
Calicat-Wayns said the students benefit from more than just programming skills.
"It's a great networking opportunity," he said. "You meet a lot of people who have a lot of influence as far as college or internships and things like that, and this project allows us to get those connections."
The app won't be accessible to the general public until the students purchase an Internet domain, which is expected to happen very soon, Korostelev said.
An application for smartphones has also been discussed among other improvements, including the ability to send text messages or push notifications of crimes to users' phones, students said.
Scott, a student from Harriton High School in Lower Merion, was so eager for today's presentation that he said he would not be able to sleep.
"I'm so excited," he gushed.