iOS, Android, Web
The Couple app connects you and your significant other in a secure messaging environment, allowing you to send instant messages, videos, photos and unique emoticons, all locked away behind a pin number. If you're feeling particularly romantic, you can even 'thumb kiss' by touching screens in the same place, at the same time. It's cross platform, and even offers a web app so you can use it right from your computer's browser. Great looking, secure and beautifully designed.
Although its user interface could use a fresh lick of digital paint, the feature list of this private texting app is second to none. Alongside its secure messaging you also have a vault for locking away images, videos, notes and even passwords. Military grade VoIP calls can be made, and there are group features if you want to share messages or content with several close friends at once.
Free, with ad support
We all know we should lock our phones, but it can be more of an inconvenience than it's worth. So this app helpfully locks specific apps individually behind a pattern of a PIN. It also includes a multimedia vault, and operates just as well on your phone's functions (calls, settings, switches) as it does on apps. And if you want to automatically lock or unlock your apps based on which Wi-Fi service you're connected to, you can do that as well.
This is probably the best looking cross-platform couples private messaging app out there. It connects two people for secured instant messaging, and also packs in great couple-centric features like a shared calendar, weather updates and a private photo album. It's design is spot on, making the whole experience feel very welcoming and just like your own private space. Which is exactly what it is.
Although a lot of handsets include some form of online location checking, this app delivers some extra features for anyone who regularly loses their phone, is worried about it getting stolen, or wants to keep track of someone carrying an equipped handset. It can activate GPS remotely, report its location (including a breadcrumb trail) and can be set to activate if it leaves a pre-determined ring fence. And, of course, you can remotely wipe your phone via the app.