"Make sure you baste the turkey every 15 minutes."
Also, "no compulsive video game playing -- no more than once every half hour!"
Like the evil offspring of a kitchen timer and an alarm clock, the Every N Minutes device would a) sound an alarm at the end of a specified period
b) upon the user's
acknowlegement (tapping a button on top, say), it goes silent ... waiting.
c) After the same amount of time as it'd been set for originally, it sounds again. Not louder or more insistent or anything (it's not an alarm clock which might need to persist until you're truly awake, just a reminder about something you're supposed to do every N minutes), just again.
Interface: Two dials and two buttons, plus optional dial.
Dial 1) how long is the interval? (Ex: turn it to "90 minutes.")
Dial 2) over how long a period should this last, overall? (Ex: turn it to "4 hours.")
Button 1) (recessed, on bottom or back) = START / STOP.
Button 2) (on top, easy to hit) = ACKNOWLEDGE, KEEP TIMING
Optional Dial: volume. Kitchen timers are often too loud for next to the head, and too quiet to hear from the next room over, at least if it's slipped your mind that you're timing something and suddenly it's 3 o'clock, muffins all burnt.
All 5 variables could be controlled otherwise, like with up / down thumbable controllers and an "OK" button, but ... dials are easier to figure out, IMO, at least if well labeled.
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I said this isn't an alarm clock, but it sure would be better for regulating snooze time than are most alarm clocks, which (counterexamples welcome) don't generally let the snoozer choose the length between reminders. My phone's built-in alarm has a 10-minute snooze function, my Phillips beside alarm is 8 minutes, and I've seen snooze ranges from 6 to 11 minutes. What about 15?!