In the time of Hazrat Mahdi (as), A Muslim in the East will be able to see his Muslim brother in the West, and he in the West will see him in the East.
(Bihar al-Anwar, Vol. 52, p. 391)
This hadith refers to the technological advances and visual communications systems that will arise in the End Times. People are easily able to see and speak to friends anywhere in the world by means of video phones, televisions, satellite and other forms of communication. Our Prophet (saas) spoke of this technological development 1400 years ago and said that Hazrat Mahdi (as) will come in this time.