That's not a title I toss out lightly, but Glympse  deserves it. Since smartphones first made Google maps mobile, no single application has offered so much practical functionality. Not only that--Glympse might be the only one that manages to take full advantage of that elusive little A-GPS sensor inside your device. But enough plaudits. Here's what it does.
Glympse is meant to replace the volley of "where are you?" texts and calls that punctuate your travels. Instead of constantly updating your friends on your whereabouts, use your phone to send a Glympse (via text or email) to their phone or computer, and they'll be able to track you for a pre-determined period of time. Of course, it's free.
Compared to Loopt or Google Latitude, this location-sharing app does two crucial things: first, Glympses are viewable on any phone with Web access. You'll need a smartphone app for sending them (the one for Android is out already ; iPhone, BlackBerry and Windows Mobile are in the works), but any dumbphone with a browser can use the service. Secondly, it only sends your location out when you tell it to, and only to people you specify, cutting down on the creepiness factor and the hassle of managing "friends" or permissions.
Last week I spoke with Bryan Trussel, Glympse's founder. He spent 16 years at Microsoft working on everything from games to interactive television before defecting with two Redmond colleagues to found Glympse. What's stunning about Glympse, however, is its notably un-Microsoftian feel; the Web interface is simple and polished, and the functionality is see-it get-it intuitive.
Bryan gave me the opportunity to tool around with Glympse's yet-unreleased iPhone app. Right now, the iPhone is the weakest platform for the app, because Apple doesn't allow apps to do background processing. That means that as soon as you exit the Glympse app, your trail goes dead to anyone following you. This may be solved in iPhone OS 3.0, should background applications be allowed, as rumors foretell.
When you fire up Glympse, you see your location on a map. (Here I am, in my natural Brooklyn habitat.) When you send out Glympses, you have the option of entering phone numbers or email addresses, or choosing them from your address book. You can put several recipients on each Glympse.
Once you decide to send a Glympse, you're asked to fill out a few parameters: you can add a note about your destination, choose your viewability window (up to four hours), or name your Glympse (ie, "Boston trip").
The iPhone application makes use of all the interface gadgets iPhone users have come to know; below, the duration time is selected on a rolling wheel.
Once you send your Glympses out to your friends and family, you can track each of them in your History tab and see how many views each has garnered. Since Glympse sends out a simple Web URL, people can forward your Glympse to other interested parties, so don't be surprised when a few extra views show up in the viewlog. As you can see, no one has viewed my Glympses. However, any feelings of loneliness are ameliorated by the coolness of what happens next.
Once the Glympse is sent, it appears as a text and/or email message to your friends. On their phone or computer, they can click a link to follow me, and the map updates itself regularly.
On a PC or Mac, the Glympse interface mashes up with Google maps, which can show you the person's location and travel path in either Map or Satellite (or both) modes. There's zooming as well as a time and speed tracker. Note that Glympse thinks I'm going 8MPH while I'm stationary at my desk; A-GPS modules are far from scientific in accuracy, but they get the job done.
Once a Glympse is sent, you have remarkable control over how people see your location. You can pause tracking if you so wish, or you can cancel any Glympse at any time. Trussel says that Glympse, which is venture-backed, doesn't have plans to monetize just yet, but even more capable functionality might someday be available for paying subscribers.