A freshman girl stumbles glassy-eyed at a crowded party, and a guy steps in, leading her upstairs to his room. Maybe a couple of people notice, and wonder: “Shouldn’t her friends, whoever they are, walk her home?” then turn back to their conversations.

Soon, some students at Carnegie Mellon hope, bystanders will have an easy, anonymous way to ask her friends if everything is okay, and head off some bad situations.

There’s national concern about the prevalence of sexual assault on college campuses, and lots of people trying to prevent it – there are efforts to teach students to be aware of the risks, to be careful, to ensure that they understand how important it is that both people say “yes.”

The students at Carnegie Mellon took a completely different approach. They looked at date rape as a market challenge, an unmet need waiting for a product to combat it, according to Donna Sturgess, the Integrated Innovation Institute’s executive in residence. So instead of trying to educate the people involved, the institute’s students invented ways for people nearby to step in if something looks troubling, with mobile apps that let people anonymously send an alert.

It’s part of an ongoing effort, “Innovate Against Rape,” the slogan institute leaders are promoting to spur new ideas.

The two teams of graduate students with business, engineering and design backgrounds could see obvious challenges: How do you get someone to carry an alert system for a problem almost no one expects to have? Since they were looking mostly at cases of unwanted sex between people who were dating or acquaintances, they knew people weren’t walking into what they thought was a risky situation.

There was also the drunk thing.

“Both teams felt the victim is compromised in these situations,” said Peter Boatwright, a co-director of the institute and a professor there, “because the percentage of alcohol-related circumstances are extraordinarily high. The line on someone who isn’t capable of making good judgments [at that moment] seems like a risky tactic.”

But they also knew that people at a party or bar or dorm are unlikely to call for help or step in. Maybe they hesitate because there’s underage drinking or drug use going on. Maybe they just aren’t sure enough of the circumstances, all the complexities of relationship and intentions, to feel that they should make a call. So both teams wanted bystanders to be able to signal an alert anonymously, with less drama than a 911 call.

And they needed something students would have with them already – they knew asking people to carry another device would never work. Cellphones were the obvious answer.

One group designed an app called SPOT(A Problem), which would allow people at a fraternity party to send an alert to the brothers designated to monitor guests for problems (it would also work at bars, clubs, concerts, anywhere with people assigned to look for trouble.)

The other team wanted an app that students would want to actively use that would include a warning system. Their solution, NightOwl, creates a mobile, location-based social-sharing scene; everyone at a party could see who else was there, share photos which erase quickly, choose music playlists, trade messages.

“And then, oh, by the way, there’s this other feature that’s really easy to get to,” Boatwright said.

With NightOwl, friends at the party would get a message that designers hope would prompt them to check on the situation. Maybe it was her boyfriend, making sure she got home safely.

Or maybe they find they they need to do that.