Philadelphia is testing a new tool for keeping major events safe. In advance of the Broad Street Run this Sunday, officials trotted out SENTRY.

Joe Sullivan, chief inspector with the Philadelphia Police Department's homeland security team, says the mobile surveillance unit kind of looks like a big generator mounted on a trailer.

"Except this has a pole that extends far up into the air with one to four cameras on it," said Sullivan. "The cameras can remotely pan, tilt, zoom. They have night vision infrared so that we're able to use them on a 24/7 basis."

The units are also self-powered by solar panels.

Samantha Phillips, director of the city's Office of Emergency Management, says three of these units will be on the scene at the Broad Street Run, ready to help out with a full range of issues.

"It could be an investigative issue, but it also could just be looking at the flow of the crowd, seeing if there are problem areas," said Phillips. "Certainly if there's a medical issue it helps us, again, deploy resources quickly and efficiently."

Phillips says the Boston Marathon bombings have heightened awareness, but they are not the reason Philadelphia is deploying SENTRY.

"We were looking at this before Boston," Phillips said.

The units will be on loan to the city from S4W, the Doylestown, Pa.-based company that builds them.

SEPTA recently bought a SENTRY. It has been used to help nab thieves at one of the agency's train yards.