If we say, "Ameen" during the live prayers on television, like live telecast of Arafat prayer, we will be included in the groups saying "Ameen" on Arafat?

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

There are many Ahadith that urge Muslims to make Taamin (saying Ameen) following Du’a.  Ayisha (Radiya Allahu Anha) said: 'Jews do not envy you more as they envy you for your Salaam and Taameen'. [Ibn Majah]

Al Hakim reported from Habib Ibn Maslamah Al Fahri (Radiya Allahu Anhu) that he said: 'I heard the Prophet (Sallallahu Alaihi wa Sallam) saying: "No group of people would gather and some of them make Du’a and the others say ‘Ameen’ to it except that Allah responds to their Du’a".

All the above is an evidence that the Muslim is rewarded for saying ‘Ameen’.

On the other hand, we do not see any difference between saying ‘Ameen’ with the person making Du’a and saying it to Du’a you hear from TV, radio or cassettes.  In fact, these are only the means of carrying the voice.

Allah knows best.