Looks like we can sign up for a free service from the USGS that will alert us to any quake of magnitude 5.5 or greater. Seems pretty handy, but maybe not quite as timely as I would like (a few hours to a few days they say, depending on the quake.)
I’d like a near-real-time service that would contact me for any quake relevant to Japan. That is worth paying for. Mainly, I want to know how far away the quake epicenter is from Tokyo, how deep it is, and how strong it is. Those three factors determine whether I panic or go back to my routine.
USGS Earthquake Hazards Program: Earthquake Notification Services
UPDATE: USGS Map for Asia