If you don't want to see a grown man gush like a tween at a Britney Spears concert, stop reading.
I've been a sucker for the pairing of lat/lng based data/apps for many years. Threading location into the fabric of the web "only makes sense." From my first mashup with Google's Map API, to my Garmin Forerunner 305 (and associated activities) I've taken the Geo location bait; hook line and sinker.
The advent of a "location" API on the iPhone (firmware 2.+) warmed my heart as it coupled a device I love (and hate at times) with lat/lng. Sadly, the Apple AppStore has been shockingly slow to pickup location aware applications (aka developers haven't written good stuff, or if they have they've kept it off the AppStore). I was further blown-away at Flickr's continued inability to automatically geo locate images I take on my iPhone, into "my flickr map." That one continues to baffle me; especially given that the majority of mobile phone pics uploaded to Flickr come from iPhones.
While Loopt failed to email me when their iPhone app finally went live, I did pull it down yesterday, and I have to say it's the poster-child of iPhone integration.
Decoupling where I say I am, from the actual GPS location was brilliant. You may see where I am on a map, but I never actually reveal the abstracted sense of where I am unless I want to. Granted, you can deduce it within a few yards very quickly, the separation was a solid way of giving me control over where the software says I am, and how I characterize my location. For example, Loopt knows I'm at latX and lngY, but I get to label that how I want. That can be "in Boulder," or "at my house;" my choice. Subtle, but powerful line to draw.
Of course, full control over whether my location is automatically logged, or manual; a given when it comes to location sensing/publishing.
Integration with the iPhone's contact list and mashing it up with other known Loopt users was gorgeous. The "add friends" button gives me multiple options, one of which is "from address book." Clicking on that shows me who in my address book is already on Loopt, and I can just check them off and "invite" with incredible ease (or invite folks not already on Loopt of course). Apps like these are only interesting if a critical mass of your friends are on them (same old social app story here).
Search for restaurants/businesses has some great defaults right out of the box, and displays Yelp! reviews on map markers right out of the gate; very well done.
Fantastic UI layout with tabs illustrating just what matters to me: map (where I am, and where my friends are), list (same thing in list view), what's up (a textual/comment/picture view of what's going on, and an opportunity for me to leave a "notice"/message about what I'm up to). Clicking on various UI elements does what you'd expect. Great high-level UI abstractions and "at a glance" usefulness, with anticipated deep-dive when I want it.
Ping functionality "pings" friends: basically a way of saying "here's where I am... come join me if you want." Dirt simple, but powerful.
Messaging friends, leverages iPhone's native SMS client. Call'ing friends uses iPhone's phone. And on and on. Basically, whenever you think the app should leverage existing facilities, it does. Loopt avoided the constant pitfall of building everything yourself. As a result, it's a hallmark for iPhone, multi-service/API, integreation. You can imagine the "how do we build a great Loopt app for the iPhone" product brainstorm, and everything that got put on the whiteboard, got implemented.
Gone are the days where I have to explicitly "checkin" to a location via SMS. Too much typing. Location feels like it's just a part of my device experience now and I can choose to not say anything about where I am, or post comments about it and add pictures.
While we're all enamored with the progress of "web apps," Loopt's iPhone App is why client-side software (coupled with web services obviously) is often still the winning combination.
Can't wait to see Brightkite launch the next salvo. A high bar has been put in place.