This summer's heat has already killed 25 people in Philadelphia. A University of Pennsylvania emergency room doctor envisions a future where the power of social media could help prevent those kinds of deaths in the future.

"You could have a Facebook page where potentially you are connected with someone who lives in your community," said Dr. Raina Merchant.

Merchant sees an online buddy system that would allow elderly or at-risk neighbors to check in on each other virtually.

"You could say, ‘Well I'm going to check in on this person, and this person's going to check on me, and we can post that in a public fashion so that people know that we’re connected and we’re looking in on each other,'" Merchant said.

GPS-linked programs like foursquare could also allow people to check in with their networks, to tell them they are buying an air conditioner or alert loved ones that they need help, Merchant said.

Facebook and Twitter were an important part of relief efforts in Haiti and other disasters, and health professionals should look for ways to leverage social media sites more, she said. Merchant is part of a team at U Penn developing a smart phone application that would show the location of the closest automatic defibrillator.

"We think this has implications for finding other emergency equipment in ways that we couldn't locate before,” Merchant said.

Merchant wrote about social media networks and disaster preparedness in the New England Journal of Medicine this week. The article pointed to social media success stories, including a Department of Health and Human Services “Mommycast” that educated a million viewers about the 2009 H1N1 flu pandemic, and the intervention of community members who texted photos of oiled birds to officials after the 2010 Deepwater Horizon oil spill.

But Merchant said there is not a lot of evidence about how effective social media networks are in times of natural disaster. A large stumbling block to widespread use is that many of the most at-risk people – the poor and elderly – do not have access to smart phones or are not on social media sites.

The American Red Cross is stepping up its focus on social media. Philadelphia spokesman Dave Schrader said they are recruiting more volunteers to scour Twitter postings from people struck by natural disaster.

"Someone would go on their Twitter account using their phone and can say ‘This certain creek is overflowing, we can't get out,’” Schrader said. “A Red Cross volunteer is monitoring that and they can alert emergency responders to respond."

Merchant said it is important to integrate preparedness into applications people already use--adding locations of emergency shelters to iPhone apps that already help diners locate their favorite restaurants, for example--so people are not fumbling to learn new programs when disaster strikes.