It's fully understandable that the Pacific has a tsunami warning network because that's where most of the tsunamis happen. According to some good Discover Channel programs on the subject, tsunamis happen somewhere along the Pacific Ring of Fire every few years. However, a tsunami can happen in other places, too, as we've seen all too well. They can also happen for other reasons besides an earthquake, such as a massive landslide or even a moderate sized impactor (had 2004 MN4 hit, the energy released would've been about 4-5 times that released by the Sumatra earthquake).

We need some global warning system, perhaps as separate consortia for each geographic region or perhaps as a coordinated network. That's only part of the problem, though. Once a potential tsunami-causing event is detected, there has to be someone on the other end of the line to answer the phone. Workers at the Hawaiian tsunami center had detected the earthquake in Sumatra but didn't have any means to give a warning. Each participating nation will need some form of civil defense center with someone there 24/7. For smaller nations that may lack resources, that might be a police station or something equivalent. There also has to be some means of acting on a warning. The Discovery Channel programs show how Hawaii and Japan have created evacuation plans, conduct drills, have established warning systems, and education for the populace.

One problem is false alarms. Back in 1994, the Hawaiian tsunami center issued a tsunami warning. The alarms sounded and people were evacuated to higher ground. Civil Air Patrol planes flew over the beaches to ensure people had evacuated. Police and other emergency workers jumped in and did their job quite well. With it arrived, the tsunami was about a foot high. Between direct costs and lost business, the evacuation cost about $30 million. When (not if) the next tsunami warning is issued, will people take it seriously or will they think it's another false alarm? Since it's very difficult to predict the magnitude of a wave, there will likely be a lot of false alarms for every serious incident.