Go bare metal and make constant use of sleep modes. The less time your system is awake and running at full speed the better. There are some cool low power chi

Go bare metal and make constant use of sleep modes. The less time your system is awake and running at full speed the better. There are some cool low power chips like the Tiny Gecko: http://www.silabs.com/products/mcu/lowpower/pages/efm32tg-tiny-gecko.aspx http://www.silabs.com/products/mcu/lowpower/pages/efm32tg-ti... However you can probably get most chips down into the sub-milliamp range while asleep and run for months or more off a few batteries.