When Jeff Hookey checked his e-mail at his home in Cornwall on Jan. 22, a Saturday, he found this message:

"Metro-North will be adjusting its train schedule according to blizzard conditions. We are currently running a regular Saturday schedule. On Sunday, Jan. 23, we will run bi-hourly service making all local stops."
...
Hookey, of course, could have found out the same information from Web sites, broadcast traffic reports and customer information centers, but he and thousands of other commuters are relying increasingly on personal notification systems to stay abreast of scheduled and unscheduled disruptions to train service.