How I can collect live data about football matches?

I wonder about the ways of collecting live data about football matches like: scores, players, events (yellow, red cards, injuries).

I know that there is possibility of taking this data from pages like FlashScores using PHP, however I want to know how the FlashScores and similar services gets data to their databases. What way they collect data?

It is impossible to have person on each match :P

I wonder if they get scores from web pages of each league. Is it possible? If it doesn't generate too big network traffic?

If anyone has some ideas, please help me with this problem ;)