If you're fed up with paying through the nose to text photos or send texts abroad, mobile instant messaging could be the solution you've been looking for.
Free on iOS, OSX
For those of us who have been online for more than a few years, instant messaging is hardly new. Some of us were using AOL Instant Messenger (AIM), ICQ, MSN Messenger and others more than a decade ago, and indeed many of those old favourites are still out there, trying to keep up with a younger, more agile generation of purely-mobile IM apps.
But when Apple announced iMessage for iOS5 in 2011, it had one big advantage over its rivals: SMS integration. This makes it a one-stop shop for messaging, because when you create an SMS the system automatically looks up the recipient - if they too have iMessage installed (and if you have an active data connection), it sends as a free instant message.
Of course, this means you can only send free iMessages to iPhone, iPad, iPod Touch and Mac users - there is also an iMessage client for OSX - but if you have friends abroad using Apple gear, it is a cheap way to stay in touch. To enable it, go into Settings, Messages and toggle the switch - it will send and receive an SMS to confirm, and then any other iMessage user will appear in the SMS 'To:' box in blue instead of green.
Free on BlackBerry, Android, iOS
One of the first truly mobile IM services to make it big was BlackBerry Messenger (BBM). The fact that it was originally only available on BlackBerry handsets was good business for several years after its 2006 release, as its developer RIM (now BlackBerry Ltd) sold a lot of handsets specifically to run BBM.
What RIM and others realised was that, while the mobile phone networks had successfully sidelined the original IM generation by bundling text messages with your monthly subscription, they had subsequently botched and overpriced the roll-out of MMS - the multimedia messaging service that lets you 'text' photos. Even now, if you spend money sending an MMS to someone on a different network, they may receive an SMS telling them to log onto a website to view your photo.
BBM fixes all that, taking advantage of ever cheaper mobile data, widely available Wi-Fi, and of course smartphones to let you send pictures, videos, icons, smiley graphics, and all the other detritus that clutters 21st century communication. There is also a 'presence' element, so you can see which of your contacts are online, available or busy, and more recently it has acquired the capability for Skype-style voice or video calls over Wi-Fi.
In addition it is no longer BlackBerry-only. After several years of losing ground to Android and the iPhone, BlackBerry finally opened BBM to those phones last year. The iPhone and Android versions do not yet include everything that the BlackBerry version does - most notably they are missing BBM Voice, the option for free voice calls over Wi-Fi. (BlackBerry has said BBM Voice will be added to both during 2014.) Also lacking is BBM Channels, BlackBerry's attempt to graft a social publishing app on to BBM, although given its poor critical reception this may not be too much of an issue.
Anyone who needs enterprise-grade messaging that is always on and always connected should have a look at BBM. It may not do everything and it is certainly not an instant replacement for SMS, but it does the core stuff well and with good levels of security and privacy. Essentially, that is individual messaging, chat groups, and the ability to exchange photos and voice notes. The one caveat is that because your account is not linked to a phone number there is no easy way to scan your phone for existing BBM users among your contacts; some might see this as a privacy advantage, of course.
GO Dev Team
Android, free with ads or $4.99
Like iMessage on the iPhone, GoSMS both replaces and upgrades the SMS program on your Android phone. When you create a text message, then if the addressee also has GoSMS installed you will be given the option of sending it as a free instant message instead of an SMS, assuming you have a working data connection that is. (There is also an iPhone app by the same developer called Go Chat which supports the instant messaging side but not SMS.)
Interesting features include the option to schedule outgoing messages and automate replies, and a spam blocker of sorts, which lets you whitelist or blacklist numbers, block keywords, or even accept messages only from your existing contacts. You can also create a password-protected private inbox, and assign contacts to it; you can turn off message notifications for these contacts, or if you upgrade to GoSMS Pro you can assign fake notifications to your secret contacts.
As well as removing the ads, the upgrade adds various features, including the ability to back up all your messages to your memory card or to the cloud, send attachments up to 20MB in size, and create larger SMS groups than Android normally allows. There is also a premium theme upgrade - themes, which change the look of the app, are a big part of the GoSMS sales proposition.
The disadvantage, apart from the frequent exhortations'in'the'free version to upgrade, is that its user population is still relatively small, but if a group can agree to all sign up for it, it will save everyone SMS fees where possible while still ensuring message delivery.
Free on Android, iOS
Facebook Messenger has the advantage of being both multi-platform and coherent. Not only can you use it on your mobile and your computer, but you can see the same messages and chats on every device. That simply isn't possible with most other instant messaging programs, which store messages only on the device where they are sent or received.
It also has the advantage of size. WhatsApp may have almost 500 million users now, but Facebook has well over a billion active users - and that is even after we discount the 8-10 per cent that are fakes, bots, pets and so on. Not all will have Facebook Messenger installed, of course, but they can still be messaged via their Facebook webpages or the Facebook mobile app. There is also a Messenger desktop app for Windows 7 and a Messenger plug-in for the Firefox browser.
As well attaching photos, recorded sound clips and so on, Facebook Messenger supports free voice calls and can send messages to phone contacts not on your friends list, although for the latter you must synchronise your phonebook with Facebook and also make your mobile number public on Facebook.