Now scientists are putting more sensors in the Indian Ocean which would notify them when an earthquake appears and if it has created a tsunami or not. Also, many communication points in countries that border the Indian Ocean are trying to be established.
Tsunamis also effect the rest of the world. When the 2004 tsunami hit, the earths mass was pulled closer to the core, and the earth spun faster, making the day 3 millionths of a second shorter. Confused? Compare it to an ice skater who is twirling around in a circle and pulls her arms closer to her. She spins faster. Same concept.
Tsunamis also effect other parts of the world in many other ways. It affects the weather, and other tectonic plates in the earth. Tsunamis affect the weather by carrying large amounts of warm water across the earth, which evaporates into (storm) clouds. Earthquakes of large magnitude can also affect other tectonic plates
The whole world is connected, its all a system, so if one part of this magnificent system is disturbed, it affects the whole entire globe.