Arpadia is the communication app for iOS, Android, BlackBerry, Windows Phone 7. Your messages are pushed instantly to cross platform devices or sent by email. Email replies will be pushed back to you via Arpadia app. You can attach multiple media files (images, voice notes, videos) to a single message. Use any your e-mail account to register or easy sign in with your existing Google-OAuth account.
For sending messages and notifications, Arpadia app uses wi-fi connections and, where not available, it uses the same internet data plan that you use for email and web browsing, there is no other cost to message and stay in touch with your friends.