The cheapest and most efficient Indian Ocean Littoral Tsunami Warning System would be local warning siren systems (alert / 30mins /20mins /10mins / imminent distinctive aural alarms) activated by NOAA seismologists' warnings being throughputted to all addressees via the AFTN (Aeronautical Fixed Telecommunication Network) with a FLASH Prefix.
The AFTN sends important messages quite quickly. Beats a fax or phone-calling system.
Any comments?