A cross-platform messaging app built to mollify the text-conscious, WhatsApp lets you send unlimited messages, photos and audio notes to your friends and family over a 3G or Wi-Fi connection. (Take that, BBM.) After the app identifies you using your unique mobile phone number, every message you send using WhatsApp won’t count against your text limit. Even better, on the Windows Phone, service is free for the first 12 months of usage (though you’ll have to pony up a dollar for each subsequent year thereafter). Other robust features -- including group chat, GPS location data and automatic switching between SMS and WhatsApp -- will make your Blackberry-toting friend’s last reason to act smug disappear.
Free for first year, $0.99/year thereafter