How could I do this kind of scheduled task in AppEngine Python?
You've said that you're storing the target time in the Alarm table. So, your cron just has to run every minute (or every 5 or 10, depending on the resolution of your alarms) and check if there's an alarm matching the current time, and if so then do the action.
I have a form with a text field for entering a number without decimal
places representing an amount of minutes that will have to be added to the current time
and will be inserted into a table named Alarm.
When the resulting time comes, my web app must make an insert operation over another table.
For example, if the user enters 20 minutes, and the current time is 22:10, the result time
will have to be 22:30 and will be inserted into Alarm table. So, when the 22:30 arrives, a new insert will have to be made over the another table.
How can I do this on AppEngine using Python?