WHY would you need a couple app when you already have SMS, WhatsApp, Twitter and Skype? Intimacy, ease and safety. When you use an app that's only connected to one other person, there's no danger of accidentally sending sweet nothings to your entire Facebook friend list, or lending your phone to a friend only to have her accidentally stumble upon mushy private photos.
Couple has the credibility that comes with having been around for a while. It used to be called Pair, but changed its name after acquiring Cupple, the world's first couple app back in 2011.
It works like many other messaging apps. You and your partner sign up for the service, install the apps on your respective phones (iOS or Android) and start messaging each other.
In addition to text, photos and video clips, there's the option to doodle on the screen and send the resulting message or picture. Even better is Live Sketch, which allows couples to doodle together in real time.
Then there's Thumb Kiss, where you press a thumb against the screen and have it vibrate when your partner does the same. And shy lovers can resort to the "Thinking of you" thought bubble, which is the romantic equivalent of a Facebook Poke.
The app can be protected by its own password to keep out prying eyes.
Existing Cupple users can continue to use the obsolete service or migrate their data to Couple.
free (Basic) or US$19.99/year (Unlimited)
Avocado is relatively new, having been launched mid last year by former Google staff. But it's quickly shaping up as a credible competitor to Couple.
Its killer feature is the ability to use the service in a Web browser. This means that if you're on the laptop in the office, you don't have to fiddle with your phone to answer messages.
Most of Avocado's other features are roughly on a par with Couple. There are no video, sketch or thumb kiss abilities.
But in compensation, you get a choice of virtual hugging or kissing instead of a generic "Thinking of you" poke. You can also select photos that represent your mood and have them ready to send like emoticons. Even more useful is the ability to send Quick Notes that are customised snippets such as "What time is dinner, honey?" or "I've already walked the dog" that you can send with a tap.
The big caveat is that while the Basic service is free, it's limited to 200 photos and 5 to-do lists. Anything beyond that requires an annual US$19.99 subscription. But paying customers do get the additional ability to send pictures directly from the Web - perfect for showing off a potential purchase - as well as early access to new Avocado features.