With the announcement of Skype coming to Windows Phone OS, I think that another app that might be coming on WP OS is WhatsApp Messenger. It is a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. Currently WhatsApp Messenger is available for iPhone, BlackBerry, Android and also Nokia.
The problem that WhatsApp messenger had with the initial release of WP7 was mainly due to the lack of permissions to access the address book and the lack of Sockets on Windows Phone 7. Continue reading