Consider your odds of becoming a victim of phone theft: Last year, 3.1 million Americans had their phones stolen, according to a Consumer Reports survey. That's double the number from 2012.

Cellphone carriers haven't done enough to stop this growing epidemic, fueled by high smartphone resale values and a liquid secondhand market. Until they do, it's up to you to to protect your phone and aid police if it is stolen.

Starting Wednesday, the mobile security firm Lookout is adding a new tool for tracking down bad guys: the "theftie," a covert snapshot of someone trying to steal your phone.

It's part of an app that alerts you to suspicious behaviors on your phone, like a screen password mistyped three times. You get an email containing your phone's location and a highly unflattering look at the person holding your phone—be they Samaritan or supervillain. Theft alerts cost $30 a year, bundled with Lookout's other services that block unsafe websites.

Lookout is part of a growing antitheft industry that makes use of the fact that the phone is already a powerful self-contained tracking device. To test the best options, free and paid, I challenged colleagues to grab and attempt to reset my phone. These services all protected my phone's data and provided useful clues in my hunt, though sometimes the trail went cold.