CBS Local in Boston aggregates school closing information; last year I signed up for their text message alerts, because it was easier to stay current without having to consciously poll the site. Inevitably, I still refresh the site way too many times to figure out who else has closed, but that hardly matters. When I set this up last year, they were using hipcricket, wanted a username and password combination. It went into LastPass and I tried to use that this year to update my settings to remove Concord (son's school system last year) and replace it with Harvard (son's school system this year -- I'll have to do the same thing next fall when he switches to Littleton. Again, listen to me not complaining. At all.).
But no! Hipcricket no more. (ETA: Looks like they are using vibes.com) So I went to the site to follow the update your settings link. They asked for the mobile number (that makes _way_ more sense than a username/password combo, since the texts go to the mobile number anyway), sent the mobile number a one time PIN and I used the PIN to update my info. This is a brilliant system! I don't have to track anything at all. Honestly, I sort of feel like virtually all infrequently accessed stuff should work this way, except for the problem of losing the phone number would kind of suck. In this particular case, if I lose the phone number, I'd just re-sign up with my new number, and anyone who received unwanted texts to the old number could presumably just sign in and turn them off (altho it's not clear how you'd figure out where the texts were coming from if you didn't already know). (ETA: Apparently there's a listserv style generic way to turn stuff like this off; reply "STOP" and they should go away, or "HELP" if you want further info.)