Lypp is a calling service that uses Instant Messaging to initiate one-on-one and group calls from mobile devices and your desktop. Users sign in to Google Talk, Yahoo! Messenger, MSN or AIM on their mobile device and send commands to a Lypp 'buddy' to create phone calls. These commands send requests to Lypp's private network, which initiates a callback to the Lypp user and the other party or parties.