KnowRoaming's SIM card and sticker were designed to help frequent travelers save money by connecting to local networks. This latest feature stays true to that mission. You'll now be able to use WhatsApp for free around the world (the service works in 142 countries) if you use any of the company's products. KnowRoaming swears there's no catch -- you're not required to buy credit to be able to use the feature, and sending messages isn't the only thing you can do for free. You can make voice or video calls and send images at no charge, as well.