Not-so-secret agent builds record

[...] it's our turn, thanks to a cool app called Saga, a not-so-secret agent that helps smartphone users build a digital diary of their everyday activities.

Available free for Apple Inc.'s iPhone- and devices running Google Inc.'s Android software, Saga offers a painless introduction to "life-logging," an up-and-coming tech trend in which people use digital gadgets to record everything they do.

Using the phone's GPS, Wi-Fi wireless networking and motion-detection features, Saga figures out your location by itself, generating a constant stream of updates as you move through the world.

Saga achieves this feat with remarkable efficiency.

Because GPS is famously power-hungry, many location apps will clobber your battery.

Smartphone cameras can automatically tag your photos with the GPS location of where they were shot; lots of us turn off this feature so we can post pictures online without revealing where we've been.

[...] it works well with popular physical fitness apps.

At the end of your workout, Saga displays a summary that includes an estimate of the calories you've burned.

Or suppose you're at a Red Sox game and want to tweet a message to your friends.