Yes, it can be possible by third party software in computer and 3g in mobile.In computer third software like skype can be better media of communication method.
Single sign-on (SSO) is mechanism whereby a single action of user authentication and authorization can permit a user to access all computers and systems where he has access permission, without the need to enter multiple passwords. Single sign-on reduces human error, a major component of systems failure and is therefore highly desirable but difficult to implement.
single sign on is an authentication mechanism with session or cookie preservation, where in user is prompted only only once in a particular session with a computer s/he uses, and the same credentials are used across multiple platform for accessing different applications. it is like loging into your computer by authenticating to the domain controller and be able to access multiple intranet site. second example could to login to a singled wesite, and have same authentication used for different applications like forums, image gallery and email etc.