Whenever you try to load a short url resource on Android, one that will redirect you to the original address in the process, you will be taken to the system's default browser first before you are taken to the native application handling those links.
Say, you spot a link on Twitter that points to Instagram. Without Unshorten, activating that link opens your web browser of choice first, where the link is expanded before it can be opened in the native app.
With Unshorten, the link on Twitter is automatically resolved so that it is directly opened using the native Instagram application.
Here is how it works in detail.
Once you have installed the Unshorten application on your Android device, supported are all versions of the operating system from 2.2 on, you will notice that it adds itself as a potential handler for select short url services such as those used by Reddit, Instagram, Twitter, Google, Facebook, WordPress or The Verge.
When you tap on a supported short url, a "complete action using" screen is displayed to you. Here you need to select Unshorten from the list of available options. You can use the service only this one time, or select the Always option to make it the default handler for these types of links permanently.
You can tap on sample links that the application lists when you start it to make it the default handler for these types of links.
The core benefit that Unshorten provides you with is speed. Once you have configured your Android device to open those links using the application, you will save time each time such a link gets opened on your system as the web browser middle-man is bypassed automatically.
So who is this for?
If you run native apps for supported services, say Instagram or Twitter, and come into contact with short urls regularly, you will benefit from Unshorten as it speeds up the process of opening those links for you.
Unshorten supports a wide variety of online services that make use of short url services, and more are added by its author regularly so that any missing ones will be available eventually. If you use at least one of those services natively, and come in contact with short urls of that service, then it is very likely that you will find this app useful.