Loopt, a location-aware mobile application and social network, just announced that it will become the first third-party iPhone app that will be able to offer an always-on location service on the iPhone. From what we have seen, AT&T officially sanctioned this feature, which Loopt already offers on other platforms. Normally, apps can't run in the background on the iPhone. This is clearly a severe limitation for a lot of developers, and few developers have the clout to get around this limitation the way Loopt apparently did (Loopt demoed its app at WWDC last year).
What Loopt is Doing
While the details of this 'hack' are not quite clear, it looks like the iPhone will keep a conduit open to AT&T or Loopt's server that will continuously update a user's location via the iPhone's built-in GPS chip. Loopt is only allowing 5,000 users into this program for now. You can sign up for the test here; just note that after an initial 14-day trial, Loopt will put a $3.99 charge on your AT&T bill each month for this service.
Once this feature is active, Loopt will always know where you are and alert you automatically when you are close to a friend who also uses the service. Until now, you had to open the app and 'check in' to update your location. By running in the background, Loopt will be able to just alert you automatically without the hassle of you having to open the app - something most users are unlikely to do after trying out the app for the first time.
A number of mobile phones, including Android phones and the Palm Pre, allow apps to run in the background (and Loopt is available on most of these). Apple's push notifications only really work for apps that can already run independently on a web server and wait for an email, breaking news event, or Twitter DM to come in. Apps that use push notifications can't actually wake up apps on the phone and download location data or access any other data on the phone. Loopt, obviously, isn't actually running in the background on the phone either, but thanks to the way Loopt has implemented this feature, a user would never actually know the difference.
Other Apps We Would Like to See Doing This
The ingenuity of the hack and the fact that AT&T is allowing Loopt to route around the iPhone's limitation is interesting in its own right. It's even more interesting to think about the other services that could benefit from this service. Obviously, Loopt's competitors like Brightkite and Whrll come to mind here, but advertisers would also be very interested in location-aware services that could alert users to deals at nearby stores (though such alerts could quickly become annoying).
cross-reality apps (for the background on these apps, which are somewhat related to augmented reality apps, see our discussion of cross reality and sensors here). Services such as CenceMe, which uses the iPhone's sensors to check if you are walking, sitting, running or in a loud place, also currently need to be running exclusively on the iPhone to work.The same technique - keeping a pipeline to an app's server open - could also benefit another class of apps that hasn't gotten a lot of attention yet:
Hopefully - Apple will soon just allow apps to run in the background. While other platforms already offer this feature, none of them come close to the popularity of the iPhone or have a similarly convenient app marketplace.
What applications do you hope will use this technique next on the iPhone? Cross-reality apps? A location-aware social networking app from Facebook? Google Latitude?