It would be pretty shocking to think that anyone who’s made it to adulthood could think back and not remember a time they wished a witness was present, someone who could unfailingly back up their version of events. In this day and age, maybe that witness is a thing and not a person, a device most of us carry with us all the time: a smartphone.

That’s the thinking behind Alibi, a 99-cent Android app currently available on Google Play. Its official description says that Alibi can be thought of as “a body camera, or a personal DVR for your life.” The app works by constantly recording your location via GPS, audio through your Android phone’s microphone and still images (one per minute) through the device’s camera. If desired, it can also record video.

It dumps everything you record in this manner after it’s an hour old — unless you tap a button asking Alibi to save it, at which point it transfers that information to internal storage so you can keep a record of what you’ve just experienced.

According to co-founder Ryan Saleh, it was an idea born of a relatively routine encounter, though one that made him think about how if things went differently, he might want something to back up his account of how those events transpired.

“The way that Alibi came to be was that I was pulled over for a traffic ticket in New York City,” Saleh said to App Trigger by phone. “Two cops came up to my windshield and knocked on the windshield, and one of them’s just talking, totally normal, and the other one takes the liberty of asking me to roll down the window and sticks his head in the car and pokes a flashlight around. I’m a straight-laced person, I have nothing to hide, and it didn’t bother me that much at the time, but I was thinking about it, and was like, ‘You know, that probably wasn’t legal.’

“I never would have thought to pull out a camera and record the guy, and that probably would have caused more pain than it was worth in the situation, but the number of times in my life that I wish I was recording something — you don’t think to do it at the time, but you go back and you wish you were recording something — is outrageous. I said to myself, ‘You know, we all walk around with a device in our pocket that has a GPS in it, a microphone and a camera.'”

It was pretty simple to turn Saleh’s inspiration into a reality. It took only three days to have a functioning prototype, and less than a week to cook up a workable user interface.

Yet it was nearly six months before Alibi turned into something the team was ready to launch, because its creators wanted to ensure it wouldn’t simply drain a phone’s battery while it was doing its thing. That took a lot of testing on as many devices as possible and with as many other Android apps as possible.

Saleh explains that since Android doesn’t like when two apps ask to use the same hardware at the same time, Alibi is designed to constantly look out for other apps asking for permission to use devices like the camera. To avoid crashing them both, Alibi will give back the hardware and simply use it again once it’s freed up.

Running Alibi in its recommended mode, where it collects location data, audio and images, currently uses up about two percent of an average device’s full charge over the course of a day. Capturing video, naturally, uses a lot more, something like 20 percent. That’s still much better than when the app was first released.

“When we first started, it was about 80 percent,” Saleh said. “In the course of that six months, we got it down to what we think is an acceptable level. And of course, we’re constantly improving it. About once a week, we push a release of Alibi that’s got stability improvements and battery life improvements. For now, we’re focusing more on stability than on new features.”