I'm writing a PHP-based API around some data that is updated as frequently as once a minute, or as infrequently as once every 15 minutes. I'd like to have a cron job push alerts to end users when certain criteria is met (e.g. data goes above a certain threshold), but because my data changes so rapidly and is prone to wild fluctuations, I'm not entirely sure how to approach this. For reference, users can include, for example, people who have downloaded my Pebble smartwatch app, or my upcoming mobile phone app.
The data that I'm most interested in (which, if you're interested, is from the AC