In addition to matching apps Microsoft envisions the service would integrate one-click app purchase and installation. In cases where no match was found the service would store the request, run periodic checks, and notify the user if a recommendation became available. An additional part of the services would enable the transfer of app data, though this would be harder to implement.
The patent also mentions that the service could be used by consumers with a virtual device (i.e. before buying a new device), potentially allowing consumers to check what percentage of their apps could be transferred, thus acting as a lure to purchase. The virtual device could also be used to show simulated version of the apps in question. Theoretically, the patents notes, ISVs (developers) could provide free or discounts licenses for the new device. The migration tool might become a promotional mechanism, with apps competing for a recommendation, by providing some form of incentive (e.g. free license or content).
Here's the abstract from the patent:
A mobile application migration service is usable to receive recommendations for replacement and/or alternative mobile applications for potential mobile device upgrades. Additionally, the service may be usable to compare legacy mobile applications to potential target mobile applications and simulate operation of selected target applications on a new target device. Further, a service may be usable to provide one-click purchase of one or more target applications, one-click installation of the selected target applications, and/or one-click migration of associated user and/or application data from a legacy device to a new device. Such recommendations, comparisons, simulations, and one-click migrations may be used to facilitate migration from one mobile device to another, even when legacy devices are customized with highly useful and/or often used applications.
At this stage its worth stressing that this is just a patent application, there's no guarantee that Microsoft will follow through and create a real world product service based on all, or part of the patent. Companies like Microsoft file hundreds of patents every year, many of which never make it into a product.
Nonetheless the idea of a mobile application migration system is intriguing. At a stroke it could remove a powerful barrier to switching platforms. Keeping your apps might come to be seen as simple as porting your mobile phone number to a new operator. Of course the reality is not likely to match the vision, but anything which make it easier to switch will mean people are more likely to switch. For Windows Phone that's important because, in order for it to enjoy growth part a certain point, it will have to capture existing iOS and Android users.
Moreover Windows Phone is widely perceived to have an app gap. The absolute numbers do support this viewpoint (90,000 apps on Windows Phone, 500,000+ on iOS and Android). Even if effective app parity is achieved, it is likely that the app gap stigma will linger. It's hard to think of a better way of demonstrating that it does not exist that service that shows the majority of customers that they can keep the majority of their apps if they do switch.