Sunrise Alarm Clock?

Do you know what I want? I want an alarm clock app that detects the sunrise time (from information on the internet or device GPS), and then one can set an alarm to wake up x number of minutes before or after the sunrise.

As the days and months go by, the alarm clock can be set so that will always go off (for example) 45 minutes before the sunrise. For any amount of time. But it goes off with reference to the sunrise plus or minus minutes and or hours.

wWouldn’t that be cool?