Arduino Sleep and Wake?

I want to run a battery powered arduino, that will sleep for an hour then wake... run a few operations, then sleep for an hour again.

I have the sleep code working, but instead of using a hardware interrupt, like a physical button switch, I would like it to wake on its own after an hour.

Is there some clever way to leave a timer running that sets a pin high after an hour... to trip the wake pin... and restart my code?

I really just want to make a low power, xbee enabled device that will send out a data a few times a day, that can lat on batteries for a few months. Really the time running should be just a few seconds a day.

I know it's being looked at.

You can cheat and use an External RTC with alarm function to trigger the Arduino to wake up.

Quick scan of Digikey turns this one up:

This may help . . .
http://interface.khm.de/index.php/lab/experiments/sleep_watchdog_battery/

Longest sleep time is only about 8 sec. but you can inc a counter in the ISR and put it back to sleep until you want to do something.

Not the most efficient but I good success with it.

I did something which was battery powered and only needed to wake up periodically and take measurements. I built an external timer to wake up the Arduino once an hour. Here is the schematic that I used.

http://www.reuk.co.uk/Timer-Circuits-With-4060B.htm

Obviously, the external timer circuit requires power while the Arduino is sleeping but the amount was small enough that I still came out ahead.