Google Play Music
Original versions of the Galaxy S II were sold long before Google's cloud-based music player existed, back when music had to be "transferred" to phones using cables and suchlike.
Now your tunes can by synced inside and from the cloud, with Google's player letting you pull tracks and albums to your phone by pinning them from the menu – or you can save internal storage space by streaming everything through a Wi-Fi or 3G signal.
It'll also sync playlists created on other devices, too, which is very handy if you have a tablet and/or another phone on the go using the same Google account.
Another app to benefit from a recent Google reorganisation is the company's Google Drive storage system, which now lets users access a whopping great combined total of 15GB of cloud storage, for free, through the app's uploading front end.
Primarily designed to let users create and edit Google documents on the go, it's now been transformed into the perfect place to dump your photos and videos too, should your phone's storage space be a little tight after two years of filling it with high-res pics and video from the S II's camera.
Lookout Security & Antivirus
One of these days, one of the Android virus scandals may turn out to be genuine, so best be prepared for any possible future tech apocalypse.
The Android Lookout app checks app installs for malware, but also looks through email attachments and web downloads for nasty files, which is a much more common way for infections to get on a mobile.
It also includes a Find My Phone section, which, once activated, lets you track your mobile, and comes with a remote locking tool to shutdown access should you suspect a criminal's trying to leaf through your personal photos and pull out the best for a Buzzfeed list feature on how stupid you look.
Google's Android developers are gradually assimilating features and ideas offered by its army of third-party app developers, with the mobile giant's Google Keep doing a decent job of cloning the many note-taking apps out there that let us capture any interesting thoughts that may come our way.
The app's most useful tool is its combination of a Home screen widget and voice recognition, meaning that with one touch you can record your Alan Partridge style "note to self" about that amazing thing you just happened to think up. It also syncs everything via Google Drive, for desktop access to your mobile activities.
But if you've reached the end of your 24-month term and have upgraded your Galaxy S II to something else, why not make it into a personal home server?
Servers Ultimate does just that, turning any Android phone into your own little home and online media hub, complete with the power to run your own Email, MySQL, SFTP or torrent tracker from any old mobile.
The full version costs £5.95, but the freebie lets you set it up and get a feel for its level of usefulness and complexity.
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