LINE is a messaging app that allows free messages and voice calls. As long as you're connected to a network/internet, you'll be able to send messages and make calls easily. It's ranked top at the app store in 52 countries including Japan, Taiwan, Thailand, Spain, China, Hong Kong, Singapore, etc. I use this app almost everyday to contact friends and family who live outside of the country. It allows for easy and fun communication and there isn't a need to pay extra for international text or call.
Duolingo is an app created to facilitate the learning of languages. Its a free app that you can download on your phone, it offers Spanish, French, German, Portuguese, Italian, Irish, and a couple other language courses. Duolingo helps you learn different languages through different pronunciation, spelling, and hearing exercises. It also keeps track of how often you go online, it gives you xp points for daily visits. In the past I've used this app a lot, it helped me learn a little bit of Portuguese. I've also used this app in French class as a way to practice french everyday without using so much of my time. This app definitely requires your participation daily if you really want to improve your language skills.